I heard somewhere that the 6.0 LQ4 has the same stroke crank than the LS1, but it's spaced differently than the rest to fit the 4L80E (which my motor had) and that they also have a crank spacer between the flexplate and crank flange. I read this on another board where someone was trying to bolt a 700R4 to an LS1, and in another case, a 200-4R.

What I'm getting at is if it's possible with those parts, since LT1 T-56's can be used on early small blocks and early small block transmissions can be used (apparently) on an LS1 with these modifications, if an LT1 T-56 can be used on a 6.0 LQ4, or a 5.7 with an LQ4 crank? The bellhousing bolt pattern is the same though I'd have to drill and tap a bolt hole. Someone please correct me if I'm wrong since everyone always says it wont work, but some people have apparently done it.

Reason is that I have a mess of LS1 parts, including a complete 6.0 and a ton of rotating assembly LS1 parts, that I want to use in a swap over to my thirdgen, and I have the opportunity to trade a D&D LT1 T56 for some of them.

 

One, the crankshaft from a 5.3L (3.800" bore), 5.7L (3.899" bore) and 6.0L (4.000" bore) are the same in terms of what you are trying to do, all three are 3.622" stroke. They are just balanced differently based on the piston/rod weight differences from the three engines. Now, a 6.0L didn't come with a manual trans, maybe in the late Silverado SS. So the crank spacer is used on flexplates (not flywheels as manuals have), so the adapter will not work. I am sure you can use your LT1 T56 with a 6.0L, you will need an LSx type flywheel, but I am not certain on the clutch disc or pressure plate required. The LSx engine requires a longer input shaft to mate up to the crank pilot.