Rich,
Being a master locksmith by trade, I still have
NOS Briggs & Stratton locks here that I've been holding onto for decades. These are the same locks that were made for GM and I have them in correct GM keyways for 69 cars with original keys and coded heads. All the cores are original gm keyways and I can key them correctly. With a few complete sets left, I can key and Ignition w/ Trunk, and both factory original door locks to NOS glove box cores I have here as well.
They are all packed away at the moment but I'll dig some out in a few days here and get some pics off to you if you'd like a set. Happy to help as you've done some solids for me with parts needed.
Complete installation notes are posted in the link I made above.