Destroked 318

Hello - thanks to all who have helped me figure this Gasser motor out over the last month or so.
Ok I just purchased a 3.20 Stroke NOS
Bob Glidden crank and its on the way to GA .
Im planning on a 60 overbore or 3.97
Bore and crank accepts standard LA rods which I have a box of new H Beams so im going to have custom pistons made unless someone can come up with a formula for me on this issue .
Still running 340 Rpm heads so I have the 60ths area in chambers I can have that milled out or use it to accommodate a dome piston after all I want atleast 11.5.1 compression or and even up to 13.1 compression if I can achieve it
Thanks Chris
PS yes weight per CI class Im running with.