440 build questions and any suggestions.

That buildis fine. Nothing wrong with 516s, and properly done they will outflow 906s. That's not real hard to do. Te hypereuctectic pistons are fine. Very light, decent designs, cheap and plenty strong for most applications. FOr a cam, with mild gearing and understanding you wont be running power brakes, i would be looking at the XE274 or Crane 643801 (H-278-2). The second is much milder, but will still have a little idle to it. either one would do fine in your car, with any gear you feel like, until you get to lower ratios (say 4.10 and up with smaller tires), then it will run out of steam fast.