Tranny swap touble

[MUNYPIT70]

Halfway through the swap, I realized that yes, Chevy made bellhousings and transmissions with more than one bolt pattern (tranny-to-bell, not bell to block). I'm replacing a "granny" 4 with a smaller, overdrive unit that I scavenged from a 1981 van. I thought it was rather unusual to find one with the shifter on the side and reverse in the same place as the old grannys, but what the heck? Anyway, I must have ran across the only one ever made with a different bolt pattern, because nobody has even ever seen one, let alone have one for sale! The right side (anatomically speaking of course) is the same old same, but the left side bolt holes are close to the center and spread apart further than normal. Anybody know where a guy could find such an animal?