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Transmission Guru's! Need Help!

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Alright guys, here's my dilemma, I have a 1988 GMC Sierra with a 4.3l V6 and a NV3500 5 speeed, and I just lost 4th gear Synchro, and 3rd is on it's way.

My plan this summer is to get a 98-02 LS1 and T-56 6 speed. I was wondering if right now I could fit an LS1 t-56 6 speed in place of the 5 speed NV3500 that in there right now. I can get a used NV3500 for $500.00 but I guess the point is that that's 500.00 less towards my ls1/t56 swap, and i'd much rather pay 1000.00-1500.00 for the T-56 if I can just pull the motor when it comes time to do the swap this summer.

I heard that the input shaft is longer on the 6 speed than my Nv3500, and if that's the case, why are all 4L60E's interchangeable from 93-04? If it's possible to put the ls1 6 speed in my truck what vehicle do I want to pull the flywheel, clutch and pressure plate from? Is mine okay? Do i use the one from the 98-02 fbody/vette?

A 93-97 LT1 t-56 bolts right in correctly, so how is that different from the ls1 t-56? Could i just find an LT1 input shaft and put it in the LS1 for now and then swap back to the LS1 input shaft when i put the LS1 engine in this summer? If you guys had a choice, what would you do? Thanks Guys!

Brandon Cossette