Does anybody know what the clearance on a 69 351 W, between the rocker arm roller and valve when setting the valves?

 

69 351W factory should be hydraulic. So, there will be zero lash. Factory arms torque to around 20lb-ft. Adjustable rockers tighten to zero last, then down 1/2 turn into the piston in the lifter (basically, you want to push the lifter piston just less than 1/2 way in it's stroke).