I wouldn't do this myself, but I asked about it at a good LBS, and the price for rethreading Italian it makes a Phil Wood solution look cost-effective.

There are several alternate ways to deal with chainline, based on what OP is willing to do.

Mount the chainring to the inside of the crank arms (in the small ring position). Doesn't look Tarck, but works.

Use one of the (BMX? MTB?) rear hubs with 47.5 nominal chainline rather than 42.

Build rear wheel using a road hub with with equal or even reverse dish (no flipflop) and spread the rear stays enough to allow chainline to slide over. Spoke angle will be lower than with a tarck hub, but no worse than a road bike, for sure. This requires measurement, calculation, and good communication with bikeshop if they're building the wheel; but as long as you've set the hub spacers and cone/locknut setup for them, and the spacing of rear stays is centered, it should be easy enough.

Go singlespeed rather than fixed. Use a freehub rear hub (instead of a tarck hub) - not as kewl visually, but allows very flexible chainline with a single cog and a spacer kit.

From my experience trying to get a 42-ish chainline on a JIS road crank (Shimano 600EX 6208) using a symmetrical JIS cartridge bearing BB, 68 mm wide bracket, keeping the chainring on the outside, I'd recommend starting with the 103 mm. If it's too narrow (crank hits drive-side seat stay, for instance) then move it over using a freewheel/BB shim behind the drive-side "cup". The 103 may not work with an ISO crank anyway, but I doubt you'll find anything narrower than that.

There's no cut-and-dried solution here that doesn't require fiddling and expense, trial and error. If OP didn't want such grief, should have started with a Bianchi Pista, rather than a UO8!