On two non hemi builds I have done, milled heads, different cams, early style champion rockers on one, and Gage ultra light rollers on the other.
I took the stock pushrods, mocked everything up and was able see or better
said guesstimate the difference in length needed. Purchased the pre-cut
chrome molly ones from Go Power Sports ( available in several lengths )
and both engines have been running strong for a couple of years now.
You already have the stock ones, it's worth taking a look.