So, I bought a complete t56 swap kit from a guy on here, and have had nothing but problems, but that's another story.

Turns out he had the wrong flywheel, it is externally balanced, for a 400, and is a Centerforce Billet Steel Flywheel.

But it is NOT for a LT T56. It isn't "deep enough" (it's only been resurfaced once, and very lightly, so that's not it).

The hub of the clutch disk actually HITS the flywheel bolts!

Also, the "back side" (engine side) is flat, not shaped, like the t56 ones.

I need to sell this thing, but I don't know what it is!

Thanks!

 

Well, it's either 14" 168 tooth, or 12.75" 153 tooth.
I assume from the picture it's 153.

Also assuming it's balanced for a 400 (and not a 454,) there's only one Centerforce flywheel on Summitracing that matches those criteria and that's a 700107. But, Centerforce has products not listed on their site, let alone Summit's site.

Posting pictures of the back can only help. And calling Centerforce has been painless in my experience.

 

It's 153 Tooth.

It fit inside a lt t56, but it only worked because the clutch he gave me with it was a weird non-sprung hub clutch (it was small enough, barely, to fit).

I'm assuming it's balanced for a 400, because it didn't vibrate on my 400...

 

The 89-96 vette disc. has an unsprung hub because the flywheel was sprung-hub.
You then need to adjust the fork pivot height and still have a solid disc clutch which I woulnd't run on the street.