If you must split it, could I suggest two posts:

1) Engine, drive train - including engine, transmission, chassis, brakes, suspension
2) Body - Body, top, trim, lighting, seat heater/motor repairs, etc.

THe first post would, I guess, still be probably a lot larger than the second but I'd think it would take enough away to resolve the issue.

Or maybe:

1) Engine, drive train - including engine, transmission and rear end
2) Body - Body, top, trim, lighting, seat heater/motor repairs, chassis, brakes, suspension

I've had to LOOK and LOOK to find the entry I want - but it's still a link I keep on my computer for quick reference. A LOT of information in a VERY small space there.