273 adjustable rockers need refurbish.

If you had solid lifters, you'd be writing about not having enough valve lash for the pushrods you're using. Any lash is hydraulically corrected with a hydraulic cam, but you're seeing wild preload swings from lifter to lifter. Lash caps sit on top of the valve stem, under the rocker and take up the slack from the mismatched valve tip heights.

This isn't supposed to be gospel on how to build an engine but it would work, like other ideas. At least youd have consistent rocker arm geometry (as consistent as 1960's get).

I fucked up before and bought pushrods before taking measurements and it sucks. Wasted money. But I learned a lot. I always measure with an adjustable pushrod, measure the max lift the valve will obtain using the rocker adjuster and use the adj rod to take up all slack, then witness the sweep pattern over the valve. Then measure and buy that pushrod.

Sucks that the valves aren't at a consistent height and this is the root problem. Either get the heads worked, use lash caps to correct the heights, or use the adjusters and pushrods you have. I'd say there is a great chance you'll have to buy new pushrods anyways.

Unfortunately, pushrods should be the last part you buy because you need the proper measurements first instead of trying on making xyz pushrod fit.