In the past all gm cars had 3 bolt holes in the TC. The only ones that had 6 were diesels and 3/4 ton and above trucks. My SS (with 4L65e) only has 3 bolt holes and has been fine. I guess it's too late now but I would say if 3 hole lines up you are good. I have ran 3 bolt TC's behind the big block in my chevelle. Sorry I caught this late.

Dave