My 360 build.

keep us posted
post up your mechanical compression then your cranking after you get it broken in
we can all learn something and as you can see you are not the only one going through this analysis
I'd use the thin gasket as I said above
use the correct lube on the head bolts and retorque them
those that don't IMHO are the ones that have the problems and NEED a composition gasket
we used to run shims with copper coat or aluminum spray with Stage III wedge compresion
use google for spray vendors like Grainger, Competition Products - should be someone in Canada
cheers