273 rocker arm adjustment

BTW, I have been looking at your pix of your shafts.... I can see a semi-circular 'notch' that is only a partial depth into the casting, and is not in the normal position as the stock notches. The original notches are fully through the shaft and directly inline with the bottom holes. So these are not original shafts. I can't see if you have the 2 holes or just 1 per rocker, and where the holes are.

BTW, it is NORMAL for a hydrualic lifters to not compress much or at all once they have operated for a little while. If you stops the engine and let it set overnight, none of the lifters ought to compress when they are on the heel of the lobe; the built-in check valve should prevent any oil escape from the inner chamber and should hold the lifter piston. But, nowadays, you will probably find a few that will. The quality appears to have gone way downhill.