your chances of getting a real answer would go up if we knew what motor you are working on lacking that information , i will say sure the old pushrods will be fine. give them them a try , if you break something let us know
Ahh, you're apparently sorta in the wrong place here. This isn't a muscle car/ street rod/ rat rod site. Hang out, read some posts, get an idea of what this site is all about. Or put on your flame suit... Many of the guys here have never owned a pushrod.
Generally you use guide plates along with the roller rocker. If you have to have the guide plate then you'll need hardened pushrods. The length will still be 7.800, the pushrod material is different to withstand contact with the pushrod guide plate. So the answer is 'yes'
You won’t know until you mock it up and do a check. Magic marker on the valve stem top and turn the engine a couple of revolutions. You want to look for the narrowest pattern on top of the valve that stays in the center of the stem. Cam profile, lifter design, rocker design could all cause changes. SPark
never used different push rods or guide plates in our 7200 rpm race engines nor in our 402 bb tow vehicle.no problems found on yearly tear downs on race engine