Custom pushrods, how much stock lifter preload?

Keep in mind that IF the lifters were to pump up, those valves are moving closer to the pistons. Don't let them use up all your PV clearance,lol.
I used to run 1/4 turn, but had to increase it a little, cuz it doesn't take much and things get noisy. So I went to 1/2 turn or so on the rockers. At 28 threads per inch, 1 turn is .036 ..... so I run ~.020 with Hd circlip lifters. This makes them run almost like solids and I don't worry about pump-up.
If you are running .548 lift,then you must be using some HD springs. Some guys here on FABO, have had the unfortunate experience of seeing a pushrod or two punch thru the stamped rocker(s).
Jus saying.
Heck... that happens all of the time on stock engines.