Rams are from the vehicle expansion pack. If you just want to be able to hit as many things as possible, put an extra layer of heavy duty frames on the front of your vehicle, then cover them in military composite armor and heavy duty quarterpanels. That should give it the maximum durability. If you want pure damage, you want the steel rollers which may or may not also be from the vehicle expansion pack.
You can only have one layer of armor plating.