Per the SEC media guide, we've won 9 division championships dating back to 1959.
If you watch Thunder and Lightning, you'll see western division championship banners for 1948 and 1949 as well. Those aren't in the media guide, I guess because "composite standings were kept," but the division champions played a best-of-five series for the title.
Also of note, there were divisions from 1953-1958, but the champions aren't listed, but are noted in the overall results. We won the West in 1953, but lost the championship series.
Bottom line: we have won 12 SEC Western Division titles.