I have been searching the internet in search of this answer and I can only find vague answers: Can an LS1 T56 be made without too much trouble to fit a sbc/LT1 style block? If so, how and is there a company that sells the parts to do this? I have heard either the bell housing or input shaft can be changed? I have rebuilt my T5 so opening one up to change a shaft is doable. On the Chicago Craigslist you can find an LS1 complete T56 transmission for under a grand every week.

 

Bearing preload is very important when changing the front plate and input to LT1 parts if you go that route.

If a bellhousing spacer is used, the LS1 slave will actuate a T5 clutch. There may also be a shorter CTS-V slave option; I haven't looked into that.

Weir might still make their setup.

The adapter plate + T5 bellhousing is another option.

Anything that adds length to the transmission setup is going to require a shorter driveshaft and probably crossmember modifications.

Two things to keep in mind when buying are that the high mile T56 for under a grand will potentially need a similar amount of parts to be tip-top. And, getting the bellhousing & pedals is pretty important.