69 or 70 the holes are all large diameter for the input of the tranny, 72 and older are iron, all of them, 4 and 3 speed both, and thery all had two mounting pads and a crossmember directly under them this was technicaly called the rear engine crossmember and mounts per GM exact wording
they do not have a place for screw in ballstud however, as the 72 older trucks used a Z bar bracket that bolted to engine block with two large bolts threaded right into engine block,
the 6 cyl used a single stud threaded right into the block however, just like the real old cars did
the iron housings used a three bolt starter nose in which was also cast iron
it is unique one of a kind 72 older trucks and are all for large flywheel 168 tooth
5505 is the last four numbers of the casting number on trhe bellhousing if its the large hole one that you will need in order to bolt a 69 or 70 and later tranny to, they still real common in most regions, but getting fewer and fewer
good luck