I"m not sure what a bus core engine is worth ($100-$300 depending no condition) the used webbers should be about the same, again it dedends on the condition. The bus heads will need extensive rework to use on the street/track engine you are looking for. You might be better off finding some 1.8L or 2L 914 heads. You should call Head Flow Masters and get their advice on the heads and send the heads(either the bus or 914) to them for the work. If you are looking to build a street/track turbo engine, don't look to use alot of stuff other than the case from the core engine. The pistons/cylinders will have to be top self (JE/L&N) head work from Head Flow Masters or Ham Inc. a good turbo grind cam from Web Cam and I would go with L&N ceramic lifters after some of the stories I have heard and seen with type 4 lifters in the past year. As for the turbo set-up I don't have any real info on that. Don't sink alot of money in the core engine if you aren't going to use much of the stuff from it. And when you are done the webbers might be too small, If you are going to turbo it you will need 1 big carb or an FI set-up.
As far as the car,,,I agree with the "Loose the square lights and whale tail" comments. Or get the Yahn Hammer cd with the Miami Vice theme song to bast as you drive down the strip.
