What am I in for

Magnum heads won't have the heat crossover. Magnum heads won't have the same angle of intake bolt holes. Magnum heads will have blocks or pedestals for the rocker arms, not cradles for rocker shafts. You better read up a little and look at pictures so you know what your getting into. Magnum heads have been put on LA engines lots of times, but you just have to know what to expect.
Sounds like a lot more than I'm willing to do or pay for right now just trying to get this thing back on the road. I would be past the $1500 mark just to get the correct valvetrain. I can use that on better heads or stroker parts latter when I really build this thing. Right now it just needs to run. But run strong.