Rebuilding a 65 273..I need some help.

you can get 1.6 mechanical rockers new for almost less than used OEM/Isky iron ones nowadays.
Mopar Chrysler SB 318 340 360 1.6 Ratio Aluminum Roller Rocker Arms & Shafts

All the hump of the 273-4 pistons were on the spark plug side away from the closed quench portion so they will fit 302's just fine.