Magnum heads worth the effort?

300 fully loaded, ready to bolt on, and I met the member to pick them up. I chose to change to the Hughes spring kit (springs, retainers made for clearance, and keepers). Didn't put a hole lot of time into these, but it was my pleasure. I'd say I'm 600 into them with new seat.
So cool at 550 for the heads and what else do you have to do or change or buy to make them work?