Could always make a 300 or 336 out of the 273 with a 3.58" or 4" stroke lol
Since your stuck with the 273 I'd just use the stock flat top pistons you can get and zero deck add 318's 302 heads and a .040" gasket with a 500 cfm performer carb and intake and a 250 ish cam and duals and call it a day.
