Close but no cigar. The cupola is the same (at least for the later Grizz turrets), but the side plates are quite different. The Grizz is much more symmetrical. The Grizz also has 'points' at the rear side plates, the UGWS is flat. Check these out:
AAV7A1 UGWS:
photo from Ferreamole site
Grizzly:

Grizzly:

UGWS:

also from Ferraemole.
Not too difficult to scratchbuild, if you have a cupola, or sacrifice the UGWS from the Tamiya kit.
Cheers,
Jim