East Coast Marine lists vane (octopus) type impellers, but, not the earlier wobbler.
A complete later type pump is a drop in replacement
for the earlier wobbler unit. Single cylinder
models have a 12:22 gear ratio while twins
have a 14:19 ratio...they will not mix...
so look for a water pump assembly from a like
number of cylinders motor...you can remove
gear and swap, but it is very tight on drive
shaft and getting holes to line up is tough.
The above applies to Mercury K thru KD KE3
and equivalant Wizard or Sea King models.
KE4/Mark 7 and KF3 have completly different
lower units and water pumps.
Brian Wilcox has made a variety of
no longer available waterpump impellers.
(810) 794-7685 Algonac, Michigan.
There may be other vendors reproducing impellers
for various makes and models.
I think the vane type pump is a better choice for
a motor you will run...don't discard the old wobbler
assembly in case you want an "authentic" motor
at some future date.