Yeah, there's a 6 cylinder C4 that some people will call a C-9 or something. You need the unbalanced flexplate off a six, too. Inspection cover is the same as a manual. You in Oz or NZ?
Suggest you try a mockup with a BW flexplate in the C4 bellhousing, see if it works. I would feel personally happier about redrilling further from the centre than I did when slotting the six mount holes inwards 1/8".
Pretty straightforward overall but you will chase a few parts and tickle up some others, specially if choosing a column shift.
Cheers, Adam.