If you are going to use the car as a street strip car, stay away from the powerglide. The turbo 350 and 400 both have a steeper 1st gear and are actually built tougher internally. The ones that you see in more full on race cars are modified with aftermarket input shafts ,gearsets etc. To get a heavier car such as yours moving you would also need a looser converter to get the car to leave--more heat on the street.
A built 400 is tough as nails and will simply accelerate the car quickly vs powerglide because of its first gear and less of a drop between shifts.
1.82 first gear is actually a 6 cylinder piece (1.76 is stock v8)
On the street you would have to do aftermarket valve body for PG--period
With either first gear --rear gear change coming --again to make the car accelerate
your car If it were a 66 Chevy II with a aluminum head small block I would say sure but a torquey big block buick --I wouldnt.
good luck either way
500 + hp 455 (now going stage II, headers, bigger exhaust) Doug Nash 5 speed, aftermaket AC
4 wheel disc brakes,Mark williams 12 bolt, 33 spline axles, lowered,big sway bars, Metco trailing arms
Now undergoing body resto...
1997 Ford Probe NHRA Competition Eliminator B/Altered/Planetary 459 inches Olds DRCE 1260 hp on two carbs and gasoline 7.22 192 mph