This has been an old age dispute. 2 or 3 speeds. Well I have a 1968 Chevy 2 Nova with a 250/Powerglide combo, and the thing is awesome to drive. The Powerglide shifts smoothly. What do you want your car to do?
If you pick the powerglide, its a great transmission, but for instance I can go 90mph in first gear. Its probably the best for burnouts too. Although with the proper torque convertor, a powerglide can be a good racing transmission.
If you pick the TH350, the parts for them are a lot cheaper, easier to come by, and overall in a drag race, the TH350 will probably outrun the powerglide, because of its extra gear.
Although, both transmissions have the final gear of 1:1 so whatever transmission you pick, you will run the same RPM on the highway.
If I had the choice to order my car with a powerglide or TH350, I'd pick the TH350 because, I'd have a lot better acceleration.
Mind you, I'm swapping out the Powerglide for a TH2004R which is a 4 speed Auto Overdrive, I'll be running either 4.56 or 4.88 gears with my 26inch tall tire, and go along at around 2500-3000RPM @ 60mph.
And believe me with the 4 Speed Auto, and 4.56 or 4.88 gearing, It'll be very hard for people to beat me...HAHAHAHA
Peace
