Bill. Either booster will work fine.
On my 68 El Camino (since sold) I did the Cheap Big Brake Conversion as described on David Pozzi's site: here:
https://www.pozziracing.com/cheap_big_brakes.htm
He called it "theory", but I can attest it works GREAT. My trailer brakes failed one day and I had no trouble stopping even with a 5000 pound load!!!!
Corvete C3 rotors, Truck calipers; all GM parts. I used a factory master and booster from another 68.
I did a write up on Team Chevelle (may have also posted on Camaros.net) with all the GM part numbers. You re-use the drum brake spindles with mods.
Let me know if you want a link to the article. I am sure I can track it down.