It is very good already
There is 12 parts detachable in game, when car crashes you can get rid of 12 parts total, no more. Wheels are also counted to these parts.
So wheels are 4
Bumbers +2 = 6
Front grill +1 = 7
Bonnet +1 = 8
Engine +1 = 9
Mirrors +2 = 11
Last one I can't remember, maybe it was exhaust or boot lid? It is so long since I did toy with it, must do something about it.
Anyway those parts that are designed to be removable are needed to be separate objects, this is needed for getting realistic damage, if doors too are separate then one can make them be open at car selection screen, but that is bit of nonsense I think.
Problem with detaching parts to separate objects results mapping needed to be redone, I don't know if there is way to avoid this?
Also game itself needs materials to be in certain type so for example if mapping is done, material set and I put it into game, I need to make material and mapping again. I think it is possible to send material library over, but that I can do only if MJ permits it as it contains his materials. It is also possible that if you get rFactor devkit and make materials according to those instructions, then you can do mapping yourself.
I can do mapping too, but I'm sloppy person with under 1 second attention time span, results may vary, test product to not visible location before applying
Oh yes, one problem too, I think my max goes only to version 9 or was it 7?, don't know if it is possible to open new version file, I doubt it a bit, mesh itself of course is easy to transfer with .3ds format.