It's not very friendly to people who use a wheel to drive, I don't know what's wrong with it but in the Grand Marshal things are really not happy and the car just shakes uncontrollably. Using a wheel with force feedback didn't make that any better of an experience either, I'd suggest before making more vehicles you should try and fix the ones you have now
This should've been worked on more before releasing.
There are lots of shading and texture errors in the middle bits of each car, windows have some wacky shading going on, mesh needs more edge loops in the middle which is causing wack deformation, pillars have weird extruding bits, gaps in the mesh on the inside pillars, interior side is just a box with door/pillar mesh left intersecting inside, lots of texture stretching going on in the middle.
The jbeam definitely needs work as well, nodes aren't evenly spaced out with large gaps between them which cause stretching, there needs to be more node rows around the middle bit. The very long grand marshal definitely needs more nodes and is missing collision in the centre.
Should have configs too, it's lazy to not add them.