Heres the heads;
450 2.19/1.88 109.037 Similar to #3919840 with spark plug seat changed to tapered, "peanut" plug but early castings had standard, "N" reach plug. Last closed chamber cast iron square-port head. Produced in both plug designs for service replacement of 1965 through 1969 applications.
Heres a chart with piston specs;
It looks like you might be trying to use an open chamber piston in a closed chamber head,so you'll have to check for clearance.Also looks to be close to 10.0:1 cr.So a bigger cam is possible,but again you would have to check for P to V clearance.You could use a cam with a slightly wider LSA and have more lift.If you want nasty,use as big a cam as possible.