Goose,
there are a few owner's on here with cars in various stages of repair, rebuild, finish etc. We all have a totally different idea or "taste" as gary points out. There's no set rule as to how it should be finished, it's up to you. Do you want a realistic 100% accurate replica?
Do you want a "look-alike"?
A Rat Look?
A Plush look?
I rebuilt mine from what i call "a rolling wreck". I've spent a Wheelbarrow of cash to get mine to the level that I like, and what I interpret as a good looking Speedster Replica.
FYI, I bout 15 Linear Meters of Material for the Interior, but I redid it twice! My Carpeting was 5 Linear Meters, and it wasn't enough to include the Bonnet. You're not going to get drawings easily for how much of this, or that to build the car. There are some diagrams on how to finish the car off correctly, where to mount the various badges and scripts, the lights, and such, which Manny has kindly put together over the years, but other than that, it's a hands on affair. The Kit manufacturer will be able to give you a few pointers, or even sell you some really basic interior panels, carpeting kits, or even a cheap ass roof.. At the end of the day, it up to you, and what you're prepared to spend on your car.
(And I know this first hand because I asked the same type of Questions a year ago before I got mine, and Gary almost repeated what he said to you to me back then.. )
You need to do a LOT of your own research, scour the various forums, find info that will help, and then basically get in and get going.. You'll deal with the issues as and when you come across them.
Check under the "projects" section on thsi Forum at the other Speedy owner's builds, Gary's is extensive, for most of the Speedsters, mine's on my own website blog.
http://www.paterson.co.za/porsche.htm
A serious final comment is, buy as best you can, and try not take any shortcuts, and be prepared to go into this for at least 100 K.
Good luck. Keep us updated.
regards
Alan