I agree with Greg.

On the 216/235/261 mechanical-lifter valve trains, the geometry is affected very little by any length of push rod that fits under the adjustment screw on the rocker arm (and allows appropriate adjustment, with the set-screw safely/securely inside the rocker arm and the set nut safely/securing on the top of the screw). The higher lift 261 camshaft simply causes the valves to open "wider" and maybe longer.

Description of the 1954 261 engine. Almost every part of the valve train (plus the connecting rods) were beefier than on the 235; however, I agree that the 235 rocker-arm assembly, push rods, valve springs, and lifters should work just fine, unless you are going to race your engine or do a lot of heavy hauling.