I'm part way through trying to track down an actual US couterpart. So far it looks like the block ( mitsubishi G12B / 4G12) was used in pony's, and in the US 'Champ ( 80-83), and colt 140( 80-84). unfortunately, my crossover manuals are all for Euro spec stuff, and only go back as far as 1980 ( got them for sourcing parts for the Niva) so I'm having to do a lot of legwork to find the US crossovers. as of this moment, it looks like the carbs in the 48 states versions of the cars I mentioned are the same 'type', but came later in the series: they incorporate automatic chokes, and at least 2 extra vacuum ports ( 1 looks like it was for a dual diaphragm distributor setup, and the other looks like it was for some sort of high rpm emission control device) - I'm still working on the exact specs for the carbs though, trying to verify that they were, in fact, the same internals.
the 'footprint' on the carbs is the large metric standard 95mm x 45mm...same as the Niva: Dparker, you wanted a crossover list: heres a start for you, these are carbs I've personaly run on the 1.6 Niva as bolt on swaps.
Fiat/Webers - all from the DOHC 24 cylinder, 73-81 ( Weber DGV, DFAV, ADHA)
65-73 MB 230, 250, 280, & BMW 525, 528 - Zenith INAT 2bbl, vac secondary.
Ford 2.3 ( EG, 70's 4 cyl mustangs) Holley/Autolite 5200
The Zeniths were by far the smoothest carbs, but they're a PITA to tune...The Holley 5200's are common, easy to get parts for, and the easiest to tune: I also found them to be the best cold weather carbs, but thats probably not an issue for most guys 8^D
91 Niva 'Cossack', MB 240D, 4 speed auto, ~88:1 low, 30x9's, coil sprung, 830 RTI.