Can anyone ID a 275 horse 273?

hi, if you measure the bores in the intake manifold, the 275 had 1 11/16 bores. same as the holley carb, which should be on motor. check valve lift, it should be .500 lift at the valve. these are the two items that seperate the 235 from the 275 273 motors. plus it was only offered in late 1966. plus there wasn't a windage tray used. those came out in the 340 motors in 1968.