FB Carb rebuilder
 

Looking for someone to do a carb rebuild/de-clutter on an FB carb, OR, maybe, a really, really good write up on what exactly to do and I'll give it a go myself. (no, I haven't even searched)

But I'd really rather just mail it to someone and get it back guaranteed problem free and de-crapified, ready to bolt onto a car that is then going to start. Someone's already fucked with the carb in question and I don't really want to start from a not clean slate.

Any recommendations?

Well , yeah a few options I guess . I ( or someone ) could go into lengthy detail about how to modify and de-emission one of these yourself . Or you can buy a good "used" carb ready to go with the work already done .
And what year of 12A is the carb from , as later ones had more stuff on them . What mods were you thinking of , what manifold mods are you doing , engine porting , header exhaust etc. ? I have done a lot of these over the years beginning with the RX2/3 ones ( yes I/m that old:) ) . The venturies can be removed and milled , carb re-jetted and made into mechanical secondaries. I currently have two for my ITA RX-7 race car ; check the Forum on carb mods / Paul Yaw / Sterling . That may give you all the info you need .

Working on the Nikki carbs really depends on what you intend to keep functioning that was there from the factory. All of that "junk" on the carburetor was put there for a reason by Mazda. Some of it can be deleted without any real consequences, but some will cause driveability issues if other mods are not done. If you intend to do a full emissions rats nest delete than you are almost better to just swap to a Weber carb and intake.