The #991 Casting heads 1972-73 307/350 75cc Chamber Used on Trucks Heavy casting But the ones I have seen had 1.72in / 1.50ex Valves . I Like the #993 Heads Better 1972-73 They Have 1.94in / 1.50ex Valves and the same 75cc Chamber Size . That 327 Short Block can be used to Build a Nice Street Engine .