I would probally buy the heads and put them on the motor I have now and then build the new stroker short block based on the heads
I did that on my current motor, took the ported 906 off and put a set of CNC ported Eddy RPM on and picked up .2 ET and 4 MPH with the exact same compression ratio on pump gas
I increased the stroke the next winter, .050, to increase the compression ratio from 9.25 to 1 to 10.29 to 1,increased the C.I. from 512 to 518, pickup another .15 and 2 MPH
512 rock
Big C.I. motors need big heads, camshafts and exhaust systems