Yes, but I'd certainly use a smaller thread (which means new pushrods) to keep as much metal as possible. Just going from the stock 7/16-20 to the common & safe 5/16-24 saves 1/16" of re-location. The NOS late intake rocker I'm using for dims has about 7/32" (.219") from the close edge of the 7/16" thread to the end of the wide flattened pad where the adjuster nut sits. If the new thread used all of this distance, the remaining surface is not much smaller than the original. What's nice is that even though there's a bit less metal, the stiffness is increased because the distance between the 2 points of leverage (rocker shaft center and adjuster ball) is smaller.
I don't think this can be done (it's too far) because the pushrod is going to hit, and how much you can open them up is going to differ with the block, year, head etc. (not to mention you lose back 1/32" by going to 5/16" pushrods).
On the exhaust again: extra lift doesn't do much - the opening point is under 50-70 psi, and the first .020" blows it down quite a bit. How early, and how long are more important than how far (assuming you have some reasonable figure - like you get with a regrind, like .400").
The exhaust is also why you can't make new stands and change both lever lengths (move the shaft closer to the pushrod hole to prevent PR clearance problems). All 12 shaft holes and all 12 stem ends must line up.
