I think I understand your question... Just think about it for a minute. The heads that are sitting on your bench have all the valves closed.... the heads on the engine have some valves open - because the rockers have them held open, because the pushrod is pushing the rocker, because the lifter is pushing on the pushrod, because the rocker is resting on a cab lobe.... You see it? When you remove the rockers from your engine, all the valves on those heads will close too. When you put the new heads on, the valves will also be closed. When you put the rockers on, if you DO NOT rotate the engine as you go, the valves that were open before will be open again.
I guess you could, in theory, install the new heads without rotating it if you have pedistal mounted rockers (non adjustable - bolt down and torque to 25 ft lbs) but I would advise against it. It's easy to find #1 TDC if you have the valve covers off. Just put a socket on an extension at the end of a ratchet wrench and turn the crank pulley until the timing mark is at '0'.... check the #1 valves, if they are both closed, then you are at TDC of the compression stroke... If they are open, turn the engine over one more time and they will then be closed.
Install the heads, then starting with #1, install the rockers. When you are done with #1's rockers, turn the crank clockwise 90 degrees (1/4 turn) and do the next cylinder in the firing order (can't remember off hand which it is - check any service manual for firing order).
Do this 8 times (1.75 rotations of the crank) and you will have all the rockers installed properly - when the valves were closed.
Good Luck!
