Hi brettsnz and Mod CyberJack,
As far as using it on Sir Walter is concerned you shouldn't have a problem. We have a few locals around here that use SB 45's on SWB. In actual fact many buffalo owners bought Model 45's back in thy late 1960's when buffalo was all the rage. I understand that the SWB variant is a bit more of a decorative buffalo that is cut a tad higher for aesthetics more than anything else, but you should be fine.
Cheers,
BB