In my honest opinion, here are two of the most popular combos that everyone eventually builds up to before they tear into the motor.
PT6152E turbo, or PT6131RE (Same compressor wheel as the 6152 but slightly smaller turbine wheel and Garretts Dual Ball Bearing cartridge) 60# Mototron injectors, with a Turbo Tweak adjustable chip, Scanmaster scantool, good boost gauge and oil pressure gauge, upgraded intercooler (Front mount or stretched stock location) Walbro 340 255lph fuel pump, fuel pump hot wire kit, MAF pipe with Cold Air Kit, 160* t-stat, plug wires, 1 range colder plugs gapped at a tight .032 gap, adjustable fuel pressure regulator with remotely mounted fuel pressure gauge, valve cover breathers for both valve covers, PCV check valve to be used in conjunction with the stock PCV, fully built 200 transmission with either a 10" 3000-3200 stall or a 9.5" same stall lock up converter, leave the factory 3.42 rear gears alone, (this ratio has been proven to work the best with the power curve that these V6s have. 4.11, 3.90 & 3.73s are in my opinion, going backwards at this power level. Some of the fastest cars in the country that still run a factory built up 8.5" rearend, have done it with 3.42 gears, some of them with the original OEM gears and these are cars that have run well into the low 9's to high 8's) 70mm throttle body with larger upper plenum and a RJC power plate and boost control valve, 3" mandrel bent stainless steel downpipe, absolutely no exhaust leaks before the turbo, at least a 2.5" dual exhaust with straight flow through style mufflers (aka no Flowmasters, not on a turbo car) replace the stock valve springs with 100# replacements, replace the timing chain with a double roller or at a minimum a stock replacement that has a steel gear, remove front sway bar, rear suspension components with dual air bags, posi unit, lite weight wheels and either a 27" DOT bias ply or 28" slicks. On a strong, good running, correctly tuned Turbo Buick, this is a combo for low 11's on either straight race gas or alky injection with pump gas. All it basically takes it tuning the car to run the boost in the high 20ish range (24-28psi) with zero knock retard and launching the car as hard as possible by either foot brake or trans brake.
Then you take this exact same combo, change the turbo to one that has a 63 - 67mm compressor wheel and a P-trim turbine wheel, throw a set of either ported stock iron heads or un-ported aluminum heads on it, a matching ported stock intake and a small cam (206/206 - 218/218, either flat tappet or hydraulic roller) and the car becomes a monster. Especially if the turbo has a ball bearing cartridge. These are very easy and simple combos that anyone with a properly tuned stock car with a well maintained record and mileage anywhere from 30k all the way up to 110k miles can attain.
The biggest secrets with these cars is, tune tune tune and Zero detonation. Detonation kills these motors, not too mention blows head gaskets.
Most people will see that I've really stripped these two combos down to the bare essentials. And I'm sure I've left out a lot of little things. Oh yeah, one of the biggest secrets is this.......
You must have patience with these cars and treat them with respect.
These cars are nothing like your typical SBC, 5.0, LT1 or LS1. They are a breed all their own.
Hope some of this helps.
Patrick