I actually did this back in 2007 while waiting for a set of 627B carbs to be chem-cleaned & re-gasketed. I ran them for about 3 months on my 1972 500 Four with no problems.
The jet tower in the original #1 carb was corroded away. I couldn't find another #1 carb...but I had a #3 which was quite similar...
So...Being a machinist, I was not daunted by converting a #3 to a #1. First off was plugging the spigot passage on the carb body that would not be used. I tapped it to take a brass screw and installed it with Permatex gasket compound. I swapped the "L" shaped spigot on the other side for a straight spigot. Then I took the choke shaft and associated pieces off the bad #1 and substituted them on the #3.
That is basically all it took. The pilot air screw faces the wrong way (compared to the 'real' #1 carb) but that is no real problem - a long thin screwdriver can still reach it.
First pic shows the brass plug in the #3 carb body (now in #1 position in the carb 'rack'). I milled the screw flat after installing it. The second pic shows the completed 'rack'. Not much to show that it has a substituted carb.
For some unfathonable reason, the #1 carb seems to corrode more than any other (in my observations). This is an economical and simple way to substitute another carb for the corroded one. A #2 for #4 could also be done this way.
