Hypothetical 360 magnum build
as a caveat, i know just enough to be dangerous. but, the pistons will physically fit.
the pin height is probably going to be different and the ring pack/location is for sure different. with the difference in deck height of the magnum this may put the piston where you don't want it-- too far in the hole or possibly above deck. i *think* i've heard of using them as a lower cost alternative when supercharging.
if i were in your situation, i'd probably try and sell a few parts off and secure the correct pistons and rings just to make my life easier on the build and not have to potentially mess with expensive proposition of balancing the assembly.
if it's a DD and more tow mater than rickey racer, i'd go with as stock of heads as i could find. if they happened to be RT heads, awesome. if not, then whatever was cabeza du jour.