w2 headed magnum

That cam I was looking at is gone already, was a brand new comp and he sold it for 50. Was gone within 30 min. But planning on around 560-570 at the valve. So how big would you go with the cranes. I work in a machine shop, so the mods wouldn't be a problem, just looking to see what all ways it could be done. May even build our own rockers once I figure it out. Or mod the cranes for others if it was easily done.

The motor is going to be a 408, with a a518 and 3k stall going into a 66 valiant post.