Thanks! Glad the info can be useful to others.
Thank you for looking, feedback welcome good or bad.
@va Don't have the old to compare, given as core exchange. Before taking drastic measures, we decided to replaced bolts on the back plate with round head screws and it fit like a glove.
Then
we find out that the original (1991 gm goodwrench crate engine), freshly painted,
pulley bolt pattern is LARGER than that of the water-pump's mount.
....
More pics later. Lesson learned and note to self - always compare (
first) pulley with water pump pulley mount before purchase.