are these wedge closed chamber heads? how many cc's now?
if so going to that thick gasket will remove your quench and be counteproductive
I'd look at opening the chambers and/or D Dishing the pistons (is that +4 mean more cc's in the piston (i.e. add 4 cc to the volume ) or 4cc dome (take away 4ccs)?
piston guys use both terminologies
x2 on checking the surface finish (heads and block)for cometic gaskets
mopar does not have a generous crank thrust but I think this is a result not a cause
most likely not getting the converter seated in all the way
when you have it apart with thrust bearing installed chamfer the parting lines to the rear from the bearing oil groove use a bearing scraper or whatever- it's not fussy
you can also drill through the thrust into the oil passage .040 ish through the block 1/16 through th bearing and make a little oil pocker
when thrusting all the oil wants to go out the front
and do a complete cleaning- all the plugs out and brush brush brush
