My '75 Scamp 383 Build

I would tap it good with a 3/4 pipe tap put lots of RTV on the threads and install the pipe plug. Let it set up and cure good and it'll never leak. Also, 2500 for polishing a crank? I use 400 grit emery cloth and Deep Creep.

Lastly, are you actually gonna DO this project? We're growin old here. LOL