Performance 360 piston set

I'm asking because my son has a set of those, with very low miles, he had in a fresh 76 360 for ~5-6000 miles and redid it as a 408, since it drank oil ever since it was put together as a 360. I have a couple of ideas as to why that was..... And I have a mag block here that is 30 over and had an injector stick wide open and diluted the oil..... I was hoping to put the 2 together, with fresh rings gaskets and bearings.... don't have anything to put it in yet, may wind up in place of the one in my Durango which has a hi mile 360 mag in it at the moment...... Our tow rig.