I've only put on 4-5k. My transmission is starting to slip more than it used to, but it's an original 4L60e, and my truck has 196k on original engine and trans. It's held up pretty well, but I only have a 3psi pulley on it. It's definitely more powerful and A LOT more torquey. Let's put it this way: I have a stock 10 bolt with 3.73's, and I've never been able to spin the tires. With only 3 psi, I can chirp them coming off the line, no brakestand or anything. It moves pretty good. Once I do some much-needed mods (rebuild trans, headers, open up throttle body) I might throw the 5 psi on and see how it does.
Do you tow or go offroad? If not, I think I would recommend 3.73's. Lower RPM's for highway cruising, and since it would be supercharged, you wouldn't need the higher gearing for quick acceleration. It's a lot of money and work, but I think it's worth it. My kit came almost complete, and that's the key is to find one that isn't missing pieces. Supercharger, brackets for pulleys and tensioner along with the pulleys and tensioner that go on them. If it comes with the hoses for the radiator and cooling system, that would be great, but I think you could find them if you had to. There are also modified brackets for the coil and the throttle cables, in addition to an adjustable fuel pressure regulator that goes in the return line.
