Run a compression test. All clyinders should be 10-20 lbs of each other. This will check the integrity of your head gasket seal to the clyinders although the engine runs good with power? Do you loose coolant as it runs?
Considering what you have done to the engine and it is still cooking off, my bet is you have a cracked head. Chevy sixes crack around the exhaust valve seat and will cause them to run real hot.
Have a machine shop clean and magnaflux the head after you get it off.
47 Fleetmaster, Hotrod 6, 5 Speed
50 Sedan Delivery, 327, 5 Speed
| 
