Neat.
[
    {
        "type": "vehicle_group",
        "id": "VETS",
        "vehicles": [
            [ "car", 300 ],
            [ "pickup", 100 ],
			[ "suv", 50 ]
        ]
    },{
        "type": "item_group",
        "id": "vet_softdrug",
        "items": [
            ["bandages", 50],
            ["1st_aid", 10],
			["saline", 20],
			["gummy_vitamins", 15],
			["nyquil", 10],
			["disinfectant", 15],
			["vaccine_shot", 10],
			["protein_powder", 30],
			["smoxygen_tank", 20],
			["elec_hairtrimmer", 10],
			["survnote", 5],
			["mask_dust", 65],
			["glasses_safety", 10],
			["towel", 50],
			["scissors", 50],
			["fungicide", 10],
			["soap", 20],
			["chem_hydrogen_peroxide", 10],
			["canister_empty", 5],
			["stethoscope", 5],
			["scalpel", 55],
			["gloves_medical", 50],
			["medical_gauze", 25],
			["quikclot", 10],
			["hacksaw", 5],
			["gloves_rubber", 25],
			["knife_butcher", 5],
			["machete", 5],
			["rag_bloody", 10],
			["bag_plastic", 20],
			["string_6", 5]
        ]
    },{
        "type": "item_group",
        "id": "vet_utility",
        "items": [
			["dog_whistle", 10],
			["pet_carrier", 30],
			["dogfood", 30],
			["catfood", 30],
			["towel", 20],
			["soap", 10],
			["gloves_medical", 20],
			["rag", 15],
			["rag_bloody", 2],
			["bag_plastic", 20],
			["jerky", 40]
        ]
    },{
        "type": "item_group",
        "id": "vet_hardrug",
        "items": [
            ["syringe", 10],
            ["diazepam", 10],
			["antifungal", 30],
			["antiparasitic", 30],
			["antibiotics", 20],
			["thorazine", 7],
			["morphine", 50],
			["codeine", 15],
			["saline", 15],
			["smoxygen_tank", 10],
			["1st_aid", 60],
			["medical_tape", 35],
			["blood", 5],
			["vaccine_shot", 15]
        ]
    },{
        "type": "monstergroup",
        "name": "GROUP_VETS",
        "default": "mon_null",
        "monsters": [
			{ "monster": "mon_zombie_dog", "freq": 10, "cost_multiplier": 0 },
			{ "monster": "mon_dog_zombie_rot", "freq": 10, "cost_multiplier": 0 },
			{ "monster": "mon_squirrel", "freq": 1, "cost_multiplier": 0 },
			{ "monster": "mon_cat", "freq": 25, "cost_multiplier": 0 },
			{ "monster": "mon_dog", "freq": 25, "cost_multiplier": 0 }
        ]
    },{
        "type" : "overmap_terrain",
        "id" : "veterinarian",
        "name" : "veterinarian clinic",
        "rotate" : true,
        "sym" : [94, 62, 118, 60],
        "color" : "i_pink",
        "see_cost" : 5,
        "extras" : "build",
        "mondensity" : 2,
        "sidewalk" : true,
	"mapgen": [ {
        "weight": 400,
        "method": "json",
        "object": {
			"fill_ter": "t_floor",
			"rows": [
                "                        ",
                "                        ",
                "                        ",
                "                        ",
                "                        ",
                " ~~~~~~~~~~~~~~~~~~~~~~ ",
                " *--OO--OO--::--------* ",
                " *-TccccccTy..#%.c-#R-* ",
                " *-...........#c.d-sl-* ",
                " *-.ccccccT...--+---+-* ",
                " *-...........-E.#...-* ",
                " *--+---+---..-E...T.-* ",
                " *-ll-y....-..+....T.-* ",
                " *-sl-.ddd.-++---i----* ",
                " *-lt-].c..+..-rr..==-* ",
                " *----------..-#...^l-* ",
                " **~~~~~~~~;..-#...==-* ",
                "          ~-..i....^l-* ",
                "          ~-i--#...==-* ",
                "          D-.r-d...^l-* ",
                "          *-.$-]]%.==-* ",
                "          *-----------* ",
                "          ************* ",
                "                        "
            ],
            "terrain": {
                ".": "t_floor",
                "*": "t_shrub",
                "-": "t_wall",
                "+": "t_door_c",
                ";": "t_door_locked",
                "i": ["t_door_locked_interior", "t_door_locked_interior", "t_door_c"],
                ":": "t_door_glass_c",
                "O": "t_window",
                "=": "t_chainfence_h",
                "^": "t_chaingate_c",
                "%": "t_console_broken",
                " ": "t_pavement",
                ",": "t_pavement_y",
				"~": "t_sidewalk",
				"l": "t_linoleum_white"
            },
            "furniture": {
                "#": "f_counter",
                "c": "f_chair",
                "T": "f_table",
                "R": "f_locker",
				"r": "f_rack",
                "$": "f_safe_l",
                "d": "f_desk",
                "]": "f_bookcase",
                "s": "f_sink",
				"E": "f_cupboard",
                "y": "f_indoor_plant",
				"D": "f_trashcan"
            },
			"toilets": {
                "t": { }
            },
            "place_vehicles": [
				{ "x": 6, "y": 19, "vehicle": "VETS", "chance": 25 },
                { "x": 7, "y": 2, "vehicle": "VETS", "rotation": [ 2, 3 ], "chance": 15 },
				{ "x": 15, "y": 2, "vehicle": "VETS", "rotation": [ 2, 3 ], "chance": 15 },
				{ "x": 23, "y": 2, "vehicle": "VETS", "rotation": [ 2, 3 ], "chance": 15 }
            ],
            "place_monsters": [
                { "x": 21, "y": 20, "monster": "GROUP_VETS", "chance": 40 },
				{ "x": 21, "y": 18, "monster": "GROUP_VETS", "chance": 40 },
				{ "x": 21, "y": 16, "monster": "GROUP_VETS", "chance": 40 }
            ],
            "place_items": [ 
                { "item": "trash", "chance": 20, "x": 10, "y": 19, "repeat": [1,3] },
				{ "item": "vet_softdrug", "chance": 40, "x": 17, "y": 10, "repeat": [2,5] },
				{ "item": "vet_softdrug", "chance": 20, "x": 15, "y": [10, 11], "repeat": [1,2] },
				{ "item": "vet_softdrug", "chance": 10, "x": 20, "y": 8, "repeat": [1,3] },
				{ "item": "vet_softdrug", "chance": 10, "x": [16, 17], "y": 15, "repeat": [1,3] },
				{ "item": "vet_hardrug", "chance": 80, "x": 13, "y": 20, "repeat": [4,9] },
				{ "item": "waitingroom", "chance": 25, "x": 10, "y": 7, "repeat": [1,3] },
				{ "item": "waitingroom", "chance": 25, "x": 10, "y": 9, "repeat": [1,3] },
				{ "item": "waitingroom", "chance": 25, "x": 3, "y": 7, "repeat": [2,3] },
				{ "item": "cleaning", "chance": 50, "x": 20, "y": 7, "repeat": [1,2] },
				{ "item": "cleaning", "chance": 35, "x": 13, "y": 19, "repeat": [1,3] },
				{ "item": "vet_utility", "chance": 35, "x": 3, "y": 7, "repeat": [2,3] },
				{ "item": "vet_utility", "chance": 50, "x": 15, "y": [15, 16], "repeat": [2,5] },
				{ "item": "vet_utility", "chance": 25, "x": 15, "y": 18, "repeat": [2,5] },
				{ "item": "office", "chance": 40, "x": [15, 16], "y": 20, "repeat": [1,2] },
				{ "item": "office", "chance": 25, "x": 17, "y": 8, "repeat": [1,2] },
				{ "item": "office", "chance": 20, "x": [7, 10], "y": 13, "repeat": [2,5] },
				{ "item": "doctors_books", "chance": 35, "x": 5, "y": 14, "repeat": [1,3] }
            ]
        }
	}
	]
	}
]
 
Ive had it hammered out for a few hours now, but nothing I do can put one on the map unless I debug it.
Id appreciate the help making it spawn.