Nathan, I checked.
I made a typo. My 90/14 is a #2. Your #3 should be 120/14.
And I didn't read this http://www.collection-appareils.fr/a...9d3802b532215d Perigraphe's page closely enough. According to it, # 1, 1b, 2, 3b and 4 f/14 Perigraphes are all in # 3b barrels.
Re aperture blades, Ilex #3s with are much more common than #3s without. I shoot a number of lenses hung in front of the same cock-and-shoot Copal #1. The shutter is complete, has its diaphragm; I've taped the diaphragm lever to "wide open" and am happy with it. Some Ilex 3s made for tachistoscopes (the common brand is Speed-i-o-scope) have open shutter levers. Note that Speed-i-o-scopes also used Alphax #3s.
However, if you're handy enough to dismantle an Ilex, remove the diaphragm and associated parts, and reassemble the shutter, an ex-oscilloscope camera Ilex #3 may be what you need. These shutters have two drawbacks. Their rear tubes aren't threaded externally and their diaphragms don't open to the full 35 mm. I'm not sure the smaller diaphragm opening (~ 28 mm) will be a problem for a 120 on 8x10.
Re 8x10, David Goldfarb, who sometimes posts on APUG (used to, may still, be a moderator) shoots a 120/14 Perigraphe on 8x10 and has expressed satisfaction with it.