You may have a problem with using that cam and the low compression. Your slugs are going to be .090-.110 in the hole, so piston to valve clearance shouldn't be a problem. Use a thin head gasket and mill the heads as much as you can. If new pistons are and option, that's what I would do. Those are cast pistons and won't hold up to that paxton you want to put on

Or you could go with a little less duration, or degree it in 4* like on a 110 center line.