An SM420/SM465 does not compare favorable to the T-5, except if you are stump pulling. I am not trying to be a joker, but for driveability, the SM420, at highway speeds (60-75 mph) demands some high revs. out of the engine.
I have and prefer the SM420, because I am a stocker/vintage/purist (you get the picture), when it comes to my 4-5-6 Chevy trucks, but if you are looking for performance (over the SM420), a small upgrade in trannies, will leap-frog the SM420 and the T-5 is a popular/viable option.
