My old school 340 upgrades and results.

on a budget and not racing for the world championship stock rockers are fine. with the pushrod angle and slightly less than 1.5 ratio your new springs will be fine. if you go to a shop to measure bring a couple of new ones and a couple of the good used ones and installed heights. to measure lift at the valve u need a solid lifter, or a hydraulic lifter modified to solid, or a very light spring with a hydraulic lifter