2WD or 4WD? What's your axle(s) ratio? What size are your tires?
Is that city or highway MpG?
If you go with 3.73 (or 4.10, if 3.73 is not enough), your city MpG will improve, and your 4L60E will last longer too.
However, your highway MpG will stay the same (3.73), or may go down slightly (4.10).
If you've a 5plug or 4plug Vortec pcm, very seriously look into rewiring your harness to convert to a 12200411 pcm.
That pcm alone is worth MpG, no joke, not to mention the possibility of using a fully enabled Aussie operating system.