Yet another 273 build advice thread!

The one thing that jumped out is the Egge higher CR pistons with the 302 heads. Those pistons have a pop-up dome that protrudes above the deck and I just don't know of there will be any interference between those and the chamber shape of the 302 heads. That chamber is a bit differently shaped from the earlier closed chamber heads IIRC.
You'll be hard pressed to get 9.5/1 out of the present day Eggies and 302's . The chambers are very close to the same as the 273 heads.