I would look for a nice Shimano 7 speed UG/HG rear hub. The wheel bearings ride in the outer part of the freehub body moving the bearings further out for increased strength. The advantage of having a combination freehub body is that you can use inexpensive HG 7 speed cassettes. The Uniglide 7 speed cassettes still shift quite nice in my opinion and you never know, you might find a source for some - just keep your eyes open. The shift ramps on HG cassettes are usually considered better performing than the UG. Both styles use individual cogs, so building up custom combinations is possible. I’ve also read that UG cogs are the longest lasting since all but the threaded smallest sprocket is flip-able for double the life (any scalloping of the tooth profile would not cause skipping if the cog was flipped and the damage was on the trailing edge and no longer critical for chain engagement.

You mention that the 1055 and other HG ready 7 speed freehubs are more popular than the gorgeous, polished Dura Ace 7400 7-speed freehub. The good news is that this perception exists, yes. For you, this means that if you keep your eyes open you might come across a deal on a Dura Ace 7400 Uniglide hub. These are Uniglide only though which is another reason for the decreased demand. Used ones pop up pretty often on eBay, and sometimes the seller will include the matching Dura Ace cassette. I built up my 126mm Saint Tropez commuter bike wheels with the Dura Ace 7400 28 hole hub onto some DT Swiss RR1.1 rims and it built a nice, strong wheel. The 7-speed Uniglide cassette indexes well with a used 105SC GS rear derailleur and 105SC down-tube braze-on shift levers that I have mounted on MicroShift (now called Gevenalle) shift pods for a very reliable 3x7 drivetrain.

There were Shimano mountain hubs that could be outfitted with 137mm Wheels Manufacturing chromoly replacement axles, effectively converting them to 126 space road use. Deore, Deore LX, and Deore XT all came out with combo UG/HG freehub bodies for a year or two and are worth seeking out. I would have to look up the version numbers of these 7 speed Deore versions. The Deore XT hubs we’re near Dura Ace quality and came in polished silver or black anodized. They used the same design of bearing seals as Dura Ace. These bearing seals permit using a micro grease gun to service the bearings a bit without a full rebuild.

So with regard to your Campagnolo shifter/rear derailleur choice are you using 8 speed Campy? I heard that these pull 5mm per click which is the same as the Shimano 7 speed spacing (5.0mm).

I built up a 7-speed cassette on a 126 hub so I could have the smaller 12-tooth cog as the highest gear, allowing smaller chainrings for similar gearing. New and affordable freewheels will most commonly get you a 14-tooth small cog, sometimes 13.

The 7402 was Uniglide only. You’ll need a 7403 freehub body in order to run HG cassettes in 8,9 or 10 speeds. Unfortunately these are becoming hard to find. Someone on these forums called them a white Unicorn. They swap out easily using the correct splined Shimano removal tool. The 7402/7403 rear hubs were made with something like 128.5mm locknut to locknut spacing. These were a transitional design to the current 130mm standard. The thinking was that you could spread the dropouts slightly on your 126mm frame to fit. The non-driveside locknut was domed slightly to permit slightly skewed clamping in the dropouts for less than perfect fits. This was to prevent axle flexing for less than perfect fits.

It looks like our pal at loose screws is making 12t uniglide threaded cogs (34.6mm)

the others can be easily made to fit with a dremel - I’m running uniglide on 120 old bikes

If this is a steel bike, why not just use a Campy 8 speed cassette hub? I have 2 bikes that are 126 spaced with Campy 8 speed groups, including a near and dear to me De Rosa. You would get the benefits of IMO the best all around looking and performing Campy groups and not have to worry about kludging together different compatibilities.

I’m gonna be sorry I asked but I’d like to see more of that green Rossin!