I presume it's a blueprint engines crate motor? if so, it should have OEM magnum heads...cam looks to be a MP .474" cam. a cam change to a comp XE285HL with a spring change to hughes #1110 with hughes retainers would probably open up a lot of power...

that said, the RHS head flow ~25-30 cfm better than OEM magnums, so I'd swagger with no other changes you'd see a 40HP increase with the heads. the cam is the limiting factor right now, IMHO.