PMI, the problem is that the f/g/f chassis is a trashy design. Such a design will not meet current collision regulations. In order to "make a car" for sale in the US, it must undergo crash tests, collision and rollover, whereby the car is dropped on its roof. If it doesn't meet whatever specifications, it cannot be offered for sale. F/g/f's don't meet modern crash specks. These are incredibally dangerous cars in the advent of a collision. If you were involved in a collision, you would be much better off in Yugo than you would in a f/g/f. Unwary people love to preach the safety that old iron provides, but the facts prove beyond debate that old iron is death traps.
The point isn't whether or not the vehicle is roadworthy. Instead it's if it can be done leagally. The issue of roadworthy, however, does apply as far as to whether or not it's leagle. As Brett points out, there are kit cars. How does one get around the federal regulations?
I don't know what's involved with the kit cars. Brett mentions building from scratch. Does that mean steel stock, cut/weled in place? A pile of metal hand fabricated into a car is totally different. That is a true hand built vehicle.
This thing is a far cry from a hand built vehicle. Instead of the need for fabrication skills and tools, all you need is a monkey wrench and vice grips. There is no built-from-scratch with the chassis; simnply, it's a bolt together project because you are starting with an assemble chassis.
I don't know the answer, the only thing I can offer is agreeing with Jerry that I see a problem with trying to leagally register the vehicle. I had looking at hp tv/muscle car tv to see if I could find any information that mentiones the chassis. They are supposed to be experts at such things (it would be nice to see behind the curtian) and I was going to email them, asking about whether or not it's leagle to put it on the road. But I couldn't find anything other than future listings.