Pushrod length

How do I calculate the pushrod length?

Now I have:
crane hmv 282-2 cam.
Hydraulic lifters
rockerarm unknown, probably a bit stronger than stock, but in stampet steel.
Pushrods 7,5" (5/16 tube with a little bowl at the ends)
stock 1976 heads.
stock valves/springs

the changes.
comp cl 20-225-4 cam
hydraulic lifters
Sealed Power ZR862 and ZR861 rocker arms.
the heads are planed .040
Milodon 45645-8 - Milodon Street Stainless Valves 1.60
Milodon 45640-8 - Milodon Street Stainless Valves 2.02
COMP Cams 995-16 - COMP Cams Valve Springs
740-16 - COMP Cams Steel Valve Spring Retainers
Author: admin