The 1976-1979 version AMC bellhousing had a smaller window, then went larger in 1980. I don't think I've seen a post-1979 bellhousing that has the smaller window. That said, AMC may have been clearing out old stock for a time period, or it may be that a bellhousing you are being shown is claimed as one year but may, in fact, be another.
The earlier one is shown, above. The later one is shown, below.
The later one is what you want as it has the material needed for the lower driver's side hole of a GM transmission.
Any questions at all, ask. You can always upload a photo and we'll tell you what we know of your bellhousing.
