I stumbled across a Zenith universal carb which referenced the 12522 model number that have appeared in carb posts on this site and elsewhere. The supplier had an unconditional return policy so I was forced to take the plunge.
The carb arrived today. The mounting holes to the manifold match so I am over the first hurdle. The throttle and possibly choke shaft have to be trimmed to allow the carb to fit next to the block.


Will install this upcoming weekend and will advise. Keep your fingers crossed.
Bill