Zero lash is with the lifter on the base circle of the cam or with the piston on TDC on the compression stroke, the rocker arm is adjusted so there is no play between the push rod and the rocker arm. This is determined by moving the push rod up and down while tightening the rocker until just at the point the clearance is removed. With solid lifters when you get close you can spin the lifter with your thumb and index finger while tightening, and you can feel the exact point of zero clearance (zero lash). Another method I prefer for adjusting valves is the exhaust opening intake closing method. Comp Cams has this on their website, but basically its when the exhaust valve starts to open you adjust the intake valve and when the intake valve is closing you adjust the exhaust valve on the same cylinder. With this method you don't have to watch timing marks or where the rotor on the dist. is pointing.
Regarding HV
oil pumps on the 302, there are risks of breaking that
oil pump rod. I don't use the HV pump on the 302, but if you do, like Gary said, make sure to use a HD type rod. That HV pump puts a lot of pressure on that small rod. If that rod breaks all kinds of bad things happen.
