Another thing to note on the keeping it simple angle is that the 2wd pan cars, to the best of my knowledge, all use a single speed tranny, and off road type clutch systems, which are much easier to adjust and maintain.
As far as the GT discussion goes, the cars can work quite well or quite poorly, depending on tires, setup, and quality of assembly. I have seen both ends of the spectrum. I think this thread is on the right track with the 2wd pan car discussion, perhaps the GT discussion should relocate to a GT thread.