the only person that can answer your question is you... buy TWO adjustable pushrods convert one of your old lifters into a solid unit and measure after your heads have been finished off.
follow this guide, trust me its worth the effort.
A Pushrod Length & Rocker Arm Geometry "Must Read"
Finding Proper Pushrod Length - Circle Track Magazine
oh and one last note, when you do this... having a narrow swipe is better than being dead center, wide swipes kill cams and ruin valveguides prematurely.
GOOD LUCK and Let us Know.