That is quite the tallboy tandem you've acquired. I might have a J.Taylor stoker stem for you to fit on back, in the spirit of PIF, when I return home from AK. My 650b Tourist model #7590 is a bit smaller at 24/22 ST, but is nearly identical to yours minus the dynamo/integrated wiring fitments. The Reynolds butted tubing decals on mine have crumbled as well, love that Forest Green color!
I recall a lovely Campagnolo tandem Crankset w/bottom brackets of yours recently, keeping with the Specialites TA?
Just got a wheelset put together, looking forward to a bit of tandeming. I don't expect you'll have too much trouble finding a stoker.