Maybe simplify a little bit, keep the doors and windows cabin the same but have the front fenders hood grill, probably a rear opening hood, as one piece to bolt onto fabricated brackets, same for the rear. My choices one set to look like a Jaguar, formal wear more or less, kit 2 to look like a Mac truck 
Have you found any non-VW based kit cars that have alternate bodies? I canāt think of any. Itāll be hard enough getting one kit car built and runningā¦
Texases, Iām not sure I understand your question. The link I posted has lots of companies that offer non-VW based kit cars of various types. Iām sure some share chassis.
Most kit cars are rolling chassis without an engine. Not the older VW chassis with different bodies available. Others are hotrod bodies to replace steel versions. I still donāt know a ākit carā with swappable bodies on a single chassis, unless weāre talking about building a fiberglass body hot rod and putting some other hot rod body on it.
A truck chassis is an unusual choice for a sports car. It can be lowered but you will have a fake Porsche with leaf springs and a solid rear axle.
It would be easier to buy a used Porsche or three and drive the one you are in the mood for. A classic Porsche may be out of reach but there are a lot of good cars available for the money.
Kit car or any automobile project is best for someone with time to kill. If you have to pay for and rely on the spare time of others years will go by and it will be very stressful.
The chassis also has to fit the body. It seems to me that welding an aluminum tubular chassis might be the best way to go.other than that, a Bug frame might work.