I built a turbo 250 nearly 15 years ago for my son's early Nova, and it is still in use. It was pretty simple except for my choice of carbs.
I used the early Buick V6 turbos that were draw through. They were only about $300 new in the box at that time. The Original Buick manifold for this unit had a three bolt flange connected to the turbo. I built a small adapter and used the original 6 manifold. Once the turbo was bolted to the manifold, a 180 degree u-bend pipe was used to get from the exhaust manifold outlet to the turbo inlet, and another nearly 90 degree piece got us out of the turbo and headed back under the car.
Oil was supplied from the pressure sender location, run through a remote filter mounted on the firewall. The idea behind the remote filter was to help insure cool, clean oil. We just punched a hole in the pan an brazed in a fitting for the drainback.
The original turbo 3.8 had two intakes that bolted to the intake side of the compressor. One was for a 2 barrel, one used a q-jet. I choose to use a sidedraft Solex that had the same size throttle blade as the compressor intake. A small adapter took care of the hookup. After making my own needles out of brazing rod, I got the right taper to get enough enrichment when under full boost. The built-in wastegate limited boost to 7.5 lbs. Water injection was added later because my son didn't want to buy premium fuel. I put a Hobbs switch in the intake manifold set to switch at 4 lbs. Ran the power to a windshield washer unit I took off a small pickup. Putting a small brass needle valve in the waterline helped adjust the amount of water blown into the engine. I picked up the brass needle valve unit at the petstore. It was entended for use at regulating the amount of air going into small fish tanks.
All in all, the amount of time spent to turbo the engine was about a day, with another day or two wasted on sorting out the carb. If I had it to do again, I'd find the original carb to turbo intake system. It would have saved a bit of headache, although that carb is still on there without having created any problems.
