buy a good quality stall with torington bearings in it,frees up horses almost like roller rockers for your converter,also ask if they weld the stator fins all the way up or just the tips,thats important,do the jerry mod yourself and trust me your will like the 3.73 s got mine today and doing the stall next week,hope this helps
The torque converter subject is a "Can O' Worms", as the debate rages on when it comes to single disk converters vs. multi-disk setups. Whatever kind of torque converter you get, be sure to get one that uses high carbon friction material for the lining of their clutch setup. Any other material will eventually wear out, but high carbon friction will out last, and should never completely wear out. Torrington bearings, hardened input shaft, and stronger impellers are a must as well. Be sure to get one from a reputable company that actually knows what they're talking about. I have a Precision Industries stallion series converter, but I'm having to replace it, as the clutch lining is burning out, and thus the converter is slipping. When I have it rebuilt, I will have a high carbon lining put in it. Other than that, the PI converters are solid built, just they're clutch linings are crap.
As for the Jerry mod, it's the best shift kit you can put in a 4r70w automatic. I have it in mine, and love it. The only things you will need are two new valve body gaskets, a blue spring for the upper portion of the 1-2 accumulator piston, and someone with the proper drill bits to enlarge the holes in the seperator plate of the valve body. You will also need to remove the lower 1-2 accumulator spring upon install, and remove both(yes both) spring from the 2-3 accumulator piston. Be sure to referrence the tech articles for the 4r70w transmission at www.tccoa.com They have in-depth articles on the 4r70w, and the Jerry mod.
PS. If you're going to be putting in an aftermarket stall converter, shift kit, and 3.73's in the future, you better get a aftermarket transmission cooler, or you're going to fry that transmission. If you can afford it, I would get a deeper transmission pan that can hold more fluid, as this will help keep things even cooler, and a basic mechanical transmission temperature gauge, so you can monitor the transmission fluid temperature.
PS. When it comes to gears, I don't know how much investigation you've done into gears, but most of anyone on here will tell you that 4.10's are the recommended gear ratio for n/a GT's. 3.73's are ok, as my brother has them in his n/a GT, but I have 4.30's in my GT, and I love them. The highway rpms are very manageable. For planning ahead for any gear change, you will need 2qts of rear differential fluid and a 4 oz. bottle of slip additive/friction modifier. I use Amsoil 75w-90 rear differential fluid, and it's working out great so far. I don't know how many miles are on your stock rear end, but if you have a fair amount of miles, it would probably be a good idea to buy a basic install kit, and possibly a differential clutch rebuild kit. These can be had for pretty cheap.