Some time ago, we were commissioned to duplicate a 959. It started as a one piece fiberglass kit......there was a lot of cutting, but the end result turned out pretty good.
One mayor issue with these kind of body kits is that it looks ok when it is round, but when you start drawing lines on it, you realized that one side was bigger than the other
The front bottom of the doors were round off.
The fender lights were recessed.
The gutter was erased.
The two side doors were made operational.
The fuel door on the hood was free handed.
But the grafted 993 headlights instead.
Custom made plenums.
twin turbos, with manual boost controllers and fully adjustable blow off valves.
We used stainless steel tubing for the vacuum hoses because it is neater, and they use less space, we bent and flared each one of them.
Custom headers, pipes and muffler gives it a protesting voice when the traffic is it wants to go.
It is still going through some adjustments, but it has roamed the L A freeways, and so far every one who's seen it believe it is the real thing.