What would be the OEM GM part number for use at the local parts store?
Any 4-pin HEI module from the mid-1970's to the early 1980's before Electronic Spark Control came out- - - - -they're all the same. If you need to change the pickup coil it would have to be one for an even-fire V6 or an inline six like a 250 or 292, etc.
Jerry