Can anyone ID a 275 horse 273?

In 66-67 Mopar produced a D-dart with a 275 horse 273. My question is can anyone here shed some light on this motor? Like how to tell if I have one. I have a273, with 2658920 closed chamber heads, solid lift cam,full floating wrist pins,windage tray. Block numbers are C273 12-29 2806030-273-2
10-13-66. Any help would be appreciated.