What are you planning to do with the motor?

I've been running unleaded in my '64Dog since I bought it in 1984 with no valve seat recession in over 70,000 miles. I don't agree that hardened seats are necessary. I'd be tempted to put a decent valve job on the 516s and run them while saving up for better heads and pistons.
I haven't been back to the board in a while but the last memories I have of Aerohead heads was that you couldn't just buy them and bolt'em on. Workmanship had been an issue. Maybe it's better now?

R