I'd suggest before you go a lot further get the drive-train and all the turbo stuff mocked up to see exactly how long the car needs to be. The turgo, intercooler, intercooler icewater tank, waste gate, blow-off valve and plumbing can really start eating up the room, plus the fire bottles, fuel tank, chute and of course don't forget you.
I"m in the process of lengthening my car right now. First I'm getting the new engine, bellhousing, trans. drive-shaft and rearend all put together. Then I need to figure out my rad-in-a-tank for cooling and also where the turbo is going and where my icewater intercooler tank is going. I have the main water tanks in.
Then I'll cut the car in half and lengthen it to what I need.
The best of luck,
Sum