"Power" valves vs. "Spark" valves

[tubman]

I am going through a Holley 94 (model 59) carburetor for a friend. The unit appears to be in pretty good shape, but it has been sitting a looong time and everything inside was froze. I finally got everything apart with out breaking anything and am just starting to put it back together. One of the things that is stuck solid is the power valve. It has no functionality whatsoever. I went through my stuff, and found a baggie with eight valves marked "94 Power and Spark Valves". While I've been around the block with earlier 94's, I have never fooled with the later ones with spark valves on the back. Of the 8 valves I have, Nos. 1 thru 4 seem to be new unused units with no markings I can find. To the best of my recollection, these were spark valves that come with the universal kits. No's 5 and 6 have a very small "7.5" stamped in the end of the brass plunger. No. 7 has what looks like a "3" stamped in the same place, but if you turn it 90 degrees counter-clockwise, it looks more like a "(J". No. 8 is wierd, but the large end with the holes looks more like a spark valve to me.

Right now, I am leaning towards using no. 5 or no. 6 because of the stamped "7.5" and they both seem to work. Is there any way to tell the difference between power valves and spark valves, or are they interchangeable? I do a bit with power valves for later Holley 4 bbls, and those are usually marked with their opening vacuum, bu the older ones are rarely marked in my experience. Of course, all of these screw into both spark and power openings which just adds to the confusion. Any knowledge or guidance that you can provide will be greatly appreciated.