All FORD Tractors starting with the N's and continuing with the Hundred Series used Marvel/Schebler TSX model carbs -never the Zenith or Holly models. The Thousand Series may have used them - I'm not sure -but Ultradog would know that answer. The FORD TRACTOR 134 CID OHV engine used the M/S TSX 428, 580, 692, 765 carb models. 172 CID OHV engines, all used the M/S TSX 593, 706, 771, 662, 769, and 813 (4000 too) on various models. Finding anyone of these OEMs is not easy and not cheap when they are found. I can't say if your Zenith p/n is correct or not but Zenith carbs were used as aftermarket substitutes on all Ford models. I have a Zenith cross reference list somewhere but will have to look for it.
Tim *PloughNman* Daley(MI)