The adjustable pushrods have about a 1/2" of adjustment so "close" will work.

Snug down a bank of rockers. Pick a rocker and adjust it so there are two threads showing on the bottom. Get the corresponding lifter on the cam base circle. with the rocker firm against the valve, use a thin tape measure to measure from the pushrod cup in the lifter the the bottom of the adjuster. Whatever that measurement is you'll want an adjustable pushrod with that measurement at the midpoint. This will give you wiggle room either way to determine the exact length you're going to need.