Here is the line for FELTZER, as pulled from the original CARMODS.DAT file:
feltzer, nto_b_l, nto_b_s, nto_b_tw
& the line form CARCOLS.DAT (also original)
feltzer, 73,1, 74,1, 75,1, 77,1, 79,1, 83,1, 84,1, 91,1
I've yet to run into problems editing CARCOLS as long as all the cars are listed, but I know you have to watch CARMODS as I think it calls models in game.
Hope it helps.