That's actually a good question. However, the 4L60E is essentially an updated (and renamed) 700R4. The 4L80E is a modern Turbo 400. I've seen the Sy/Ty guys use the 4L80E to replace thier 700R4's, but I know as an f-body owner, the 4L80E itself won't even fit in my car. At least that's what I've heard/read. As far as the 4L60E to an LC2, I don't know if anyone's ever tried it and I've never known anyone personally to bolt up a 4L60E to a turbo Regal. So I'd like to see the answer to this myself, actually..