I'm running a 6.0 Snyder head on my 31 Coupe. The rebuilder installed the modern composition gasket and torqued to 65 ft/lbs. I have 2000 miles on the engine now with no issues. I plan to drive it from Salt Lake City to Reno in June for the National MAFCA convention. I've re-torqued the head...
It seems you have tried all the common places to look. You said the flywheel housing has been replaced and shims used on the two ears at the top behind the engine. Has the flywheel been checked for planarity with the housing? More than .010" wobble is cause for concern. Is the crankshaft flange...