If your WA2 is complete and turns over leave it original. Likely it has the poppet valve fuel mixer. They are a little fussy, but, they
did the job. Carburetor replaced poppet valve for most 1941 Kiekhaefe
Mercurys and Wizards. Converting from poppet valve to carburetor
requires changing to a magneto with a cam to synchronize spark advance
with carburetor butterfly opening as spark is advanced or retarded.
Doable....IF you have the parts. Leave it as it i....with a little TLC
and some getting used to it should run again.
The entry level 1940 Mercury and Wizards would have the poppet valve
the same as the Sea King single. Up market 1940 singles had carburetors
In 1941 Kiekhaefer changed to carburetors synchronized with spark
advance except for the Sea King single made for Montgomery Ward.
Tillotson AJ3 later AJ10 for singke cylinder models for Mercurys and
probably same for Wizards made for Wester Auto. Due to supply
problems Kiekhaefer had to wing it at times in the prewar period.
There are many variations as a resykt,