oil leaking around spark plugs flat 6

The fact that it runs decent and has no noise is a good sign as far as the low end, bearings and such. I have no experience with the flat head engines, but it sure sounds like a rebuild is in your future. I'd have to think that enough oil to bleed past the plugs means that the rings have probably seen their better days.

I want to keep tabs on this thread as a learning tool for these engines. Good luck with however things turn out. :thumbrig: