From this forum, you can post ideas for custom cars, but it must be from the vehicles list on stuff that we already have. Also in this forum, I have a list of the customizable parts for the different vehicle genres.
This list is free, everything on this list is free
Normal Cars: Wheels, wheel alignment (4WD, FWD, or RWD), suspension, engine, body paint, body armor, jet wings, jet thrusters, and mounted weaponry.
Military 4 wheeled vehicles: Wheels, mounted weaponry, body paint
Flying vehicles: Body paint
Covenant: Body paint, certain weaponry. (Ex. Ghost weaponry switched out for gatling guns)
Tanks: Treads, body paint,
Elephant: Treads, body paint, mounted weaponry
Trucks/SUV's: Tires, suspension, mounted weaponry, body paint, jet wings, jet thrusters, engine, body armor
Specialized Vehicles: Wheels (if Possible), mounted weaponry (if possible), body armor, body paint, different leg alignment (for Scarab: 4 legs, 6 legs, 8 legs)
You must post your ideas for your vehicle here for it to be approved by me and my crew, if and when I have any.
Halo: Power of the Marines