Yes, you need the correct pushrod length. You start milling stuff down .050ish, and then the guy doing the valve job fudges his work a bit and sets the stem hights on the high side (or maybe a touch more because what's .010 between friends) and we have a block that we don't know how much if any has been removed.
Then we have the cam, which may be a regrind which could have a slightly smaller base circle, or it could be a core with a with a bigger than usual (yet still in spec) base circle and you start adding it all up and you are burying the plunger in the lifter.
Or, it could be all whack and everything is on the opposite end of tolerance and the pushrods are too short, which will be highly unlikely in your case because of the milling.
The point is don't guess. Preassemble and measure everything and order the correct length pushrods.