Another piston option for the 273.
I thought of the exact same setup when i was gonna do my 273, some of those pistons come with Chevy pin size. Good thing about making a 302 you can spin about 6500 to hit 400 hp.
What you gonna use for top end ?
I was leaning towards notch block and 1.94 EQ's or heavily ported stock with ford 1.80 1.55 valves and Comps solid roller 268 gave nice curves on my desktop dyno. don't forget to make a small displacement to work you need probably at least 20% more gear than a similar built 360 or at least no smaller than 3.91.