what is your opinion this combo?

I was just going to bring that up...Domed pistons designed for an open chamber if set up properly in the block (meaning near 0 deck) will hit a non open chamber design head. I'm also curious in what your machinist told you for compression. Magnums come at 55-60ccs IIRC. With a dome, you will have much higher than 11:1. You need to check your piston to head clearance..DO NOT RUN it anymore until you pull a head and look. If they are hitting, the rod bearings need to be inspected at minimum.