I went through something kinda similiar. I was using ball/cup pushrods and Crane rockers, which require quite a bit of adjuster to show in order to get oil to the pushrod. With changing pushrod length you probably are already on one of the issues if using ball/cup pushrods, the push rod kick-out from the ball adjuster will take out lift, so the longer the pushrod the better. I was losing over .030. I went to ball/ball pushrods on my current build with the cup adjuster and have eliminated most all the kickout. I also went to a the bigger pushrod 7/16-3/8 taper, to keep down any deflection, and I am only using 400lb springs. I do think the deflection happens more than some think, from just what Dwayne described in going from check springs to your real springs you do see a difference.

I will say that like Dwayne and Andy the lift loss may not be as big an issue. I would check the scrub on what you have to see where that is, as I think this can lead to some gains if you are measuring .100 or more. The bad part is, the only way to fix is to raise the shaft. I found sometimes the rocker you use can help you out as some are shorter. When the rocker goes up it also goes out on the valve tip, a shorter rocker can help out. On mine going from a Harland to the Crane allowed me to just use a .250 spacer to fix my scrub. The motor tended to carry rpm better after that change. There are plenty of threads on here discussing it-mine is below.


https://board.moparts.org/ubbthreads/ubbthreads.php/topics/2891437/re-valvetrain-issues.html