i have a setup out of a LT1, lt1 flexplate, lt1 converter, what will i need to run this with a LS1 engine. ive searched and havent found much. is there an adapter for the flexplate to crank. or do you run a stock ls1 flexplate and get a special converter snout. thanks for the help

 

You would need to use a LS1 flexplate. If you plan on using the converter you have, you will need a crank spacer because the pilot on your converter will be to short and not seat in the crankshaft for support. Look at the sticky posts at the top of the auto section. I believe most of this is covered there. Vince

 

you can order a kit from GM, comes with .400 spacer(goes between crank and flywheel), long bolts, and flat flywheel-you may have to redrill your flywheel depending on bolt pattern of the converter
ls engines use 2 diff flywheels, same dia., but diff offsets
Hughes and some others offer adapter kits
basically, the ls crank is .400 shorter than older s/b's, so you have to make up the diff somehow
if you have an ls style engine that had a 4l80e trans behind it, it prob has the correct setup for a turbo 400
dont be surprised if your block is not drilled for the 2 o clock bolt for the trans
and you will need metric bolts to mount the trans to the block
hope that helps some
i shouldnt have had 2 cups of coffee this morn, lol

 

TCI makes a dual bolt pattern for the LS1 also

 

TH350 / TH400 / Powerglide: Everything you need to know including how to swap it into an F-Body
https://ls1tech.com/forums/automatic-transmission/815618-th350-th400-frequently-asked-questions.html

https://ls1tech.com/forums/automatic-transmission/197642-what-would-you-like-see-addressed-th400-faq.html