The F7F was powered by a two-stage supercharged R-2800, so what extra supercharger
are talking about adding? The F7F-3 version had a service ceiling of 40,700 feet, so any
big gain over that would probably be a matter of changing blower size, ratio, etc. None
of which would create much in the way of external appearance, except perhaps some
sort of enlarged air intakes. Possible, but not something that would necessarily happen
as Grumman and P&W seemed to work well together on creating extemely clean installations
in that period, which is demonstrated by both the F7F and F8F.
Stick on the long wings and just tell folks the blower system was tweeked for higher altitude.