Can't find pushrods

That should be it. If possible, measure overall. Then subtract the depth of the cup for "effective" length. The 2 ways of measuring can lead to confusion.

I believe I had used Crane 69691-16 in the past. They advertise a length of 7.33", but if that is the "overall" measurement, it may be close to what you are looking for.

Mancini may be selling them under their label here:

http://chucker54.stores.yahoo.net/enhypusech.html

But you would need to get the measurements checked. If it's within a couple of hundredths, just swap the whole set and carefully readjust the valves.