Need A Recipe For A 273 Rebuild

Hhmmm. I've never built a 273 of any kind. So this may not be the "best" thing.. but I'd go something like this:
I'd use custom pistons... mainly because in order to get decent squeeze you need them up at zero deck, and at 0 deck, you have very little room for valves. I'd also use magnum heads vs 302s. The chambers are better design and smaller. I'd also run Cometic head gaskets to set a decent quench and get the gasket bore back to a 318's 3.910. that leaves room for bore notches to help unshroud the 1.92 intake valve. You'll only ever buy them once anyway. For a cam, I'd be looking at something like the XE256H. The rockers and pushrods (for the solid cam crowd) can be sold to make soem money back. You can save $$ by buying done stock Magnum heads as they will be more than fine for the smaller cam so a set for under $800 is pretty easy to come buy. They will need to be milled to seal with Cometics, but use this to bring the chamber size down to 56cc. With a Performer intake and 500cfm AFB I think it would be a ripper. I'd bet you could have it all done, balanced, and ready to go for less than $4K with the custom pistons(I'd use Diamonds...) and Cometics. The smaller cube engines do require a little more care, but I think with more modern high velocity type heads and cylinder pressure building cam, with modern machining and design the 273 could hit 300hp under 4K rpm and have decent torque from 2500 up to hp peak. It works out to about 9.7: static, 8.2 dynamic, very pump gas friendly.