Unless the SD was an exception, Pontiac didn't sell short blocks, they sold fitted blocks. A fitted block was 8 pistons and rings in a new block. You then bought 8 rods, and a crankshaft, and all the other attendant pieces to make a short block, the labor to assemble it was your responsibility.
In the early 70s, I worked in a Pontiac dealership, and was good friends with the parts manager. As far as I knew there was no short blocks available from Pontiac in the parts channel. I suppose the SD could have been an exception since it was assembled by hand, rather than on the regular engine assembly line. I no longer have my parts books, so someone with access to them could easily look up the availability of a short block assembly.
I also noticed that the engine has a flex plate on it, doubtful it came with a flex plate on it????....
