Magnum RHS Heads horsepower gain??

Idaho said

I'm not the expert but it seems to me the power gain from just a head swap is going to be far less than what the heads make possible with the right cam and other parts.

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OK heres the combo

360 mag
crosswind dual plane
otb 650 double pumper
int 498 ex 512. int 276 exh 286 lsa 112
stock 9.1 to 1 cr
hooker 1 7/8 headers
mp dizzy
msd 6al
stock bottom end
3,91 gears
3500 stall converter
904 with reverse body

seen the same combo dyno 375 hp and 400 lbs tq (flywheel)

do you think the rhs heads OTB would add 40 hp?