Correct me if I'm wrong, but the lifter spring holds it at the extended length while it's sitting still/ not running. Doesn't really matter if the lifter is dry or full of oil. So, during initial install, shorten all pushrods to their shortest length, install, then one cylinder at a time- rotate to TDC on compression stroke, extend rods until they make contact with the lifter and then count/ measure further extention per your manual. Lock the nuts down, give it about 10 min and check to see that you can spin each rod with your fingers. It'll be a bit tight, but not frozen in place. Turn the motor over (5th gear, rear wheel off the ground, turn wheel by hand) and repeat. When all done turn it over by hand again to "proof" that there's no valve/piston contact.
On the initial startup it is helpful to spin the motor a bit- pull plugs, pull wires or however you want to do it. It might clatter a bit, but it'll stop within a few seconds.