Originally Posted by
Self loading bear
Merlin all types 41 applications according Wiki.
Pratt & Whitney R-985 Wasp 44 applications acc Wiki.
Pratt & Whitney R-1340 Wasp 56 applications
Continental C90/O-200 also 56 applications
I would expect Wikipedia's list of applications for those P&W radials and the Merlin to be pretty comprehensive.
But if we're going to include homebuilts/experimentals/one-offs (and I don't see why we shouldn't) then I would suggest that a full list of C90 applications over the last 75 years (many undocumented and/or lost in the mists of time) would run into several hundreds.