I had a set of thoise in a 383 back in the day and I seem to recall they're more like a 12.5:1 CR - and that's with an open chamber head !!

.040 - .050 in the hole and then a .060 - .070 gasket. This just sounds ridiculous to me. And it defeats the whole purpose of the domed piston. Why not take the money you'd spend on those MLS gaskets and put it toward a set of modern day, forged, light-weight pistons from 440Source that will give you the desired CR with no ridiculous effort. No fancy deck/head finish and use a standard head gasket. gasket How were you planning to get the piston .050 down in the hole - those things were made to have pretty close to zero deck height.

My suggestion is to spend a few bucks more and get your CR in a more traditional way.