273 for early A

Sounds like you should be good. I'd run flat top pistons with the 302, but have them magnefluxed before spending any money on them. Use the pop ups with the 675 heads. Make sure you have clearance between the valve springs and rocker arms. The D4B intake is great, but it is for 64-65 heads. I have an extra set of 64-65 heads if you want to run those. Assuming you have plenty cranks, rods and misc parts.