Wow Jeff, that's some picture!!! Be still my heart!!
Right now, I have a generic 4/8 ohm output transformer in it that's pretty much the size of a Super Reverb transformer, and the speakers are wired series/parallel for an 8 ohm load. Also have a repro Super Reverb faceplate on it, and a mojo repro cab.
I actually have an old Shumacher Super Reverb OT in my parts bin that I bought for it second hand, but I still haven't had that put in - I don't think I've used the amp in the last four years, the tweed Bandmasters are handier, and what I've been using most.
Totally worth it getting the speaker impedance right though, amp will sound better.
What could be an idea for yours, as I understand you're an at-home player most of the time, would be to get four 16ohm speakers for it, and keep the Bandmaster O.T. Amp will sound and perform better, but it won't be as terrifyingly loud as with a full-size SR O.T.
Four 16 ohm speakers in parallel would give you the correct 4 ohm load for the Bandmaster Reverb OT.