IMO thats really not the case at all. You can buy a lower adaptor/IC from Yella Terra that bolts right on. You can also buy a snout from Yella Terra that lines up the pulley correctly, and also offers bolt on L67 pullies in various sizes in shelf stock. Then PRJ can make a bolt on throttle body adaptor for a regular 90mm TB, and you can pick up fuel logs at PRJ or ZZP. Only thing left would be connecting up the bypass from the LIM to the TB adaptor, and setting up your BBV system.

Its not as hard to do as many people make it seem, its just that there is a lot of cost in doing one once you add in supporting mods.

 

A top swap would suffice if the numbers can be roughly 375 at the wheels using a gen 3 or Gen v blower a cam , and maybe some methanol injection/ turbo I would have gone with the l-32 converted over to the turbo kit and I definitely would have been over 500 at the wheels now for the 4t65e and HD version trans they both are rated @ 350 one has heavy duty differentials. Where I have seen some Transmissions fail is using the 300M input shaft and have too much power in the car and snapped their input shaft in there that's what I see the 300M input shaft is only rated for so much and once you go over the rating and brakes transmission failure I don't know if GM still has there 1200 horsepower rating input shaft that GM used to have I would use that if I could 3.29 gears most should I have it in my 01 Monte Carlo , trans kits have them up to 3.69:1

 

This thread is 7yrs old lol, the input shaft is weak but so is the chain set, Pump shaft, clutches, etc. If you want a trans to hold power you need to do it all and not just one part.

Gm no longer makes any of there gmr parts for the 4t65e. They have not made them parts in years and years. I got lucky any have them all though