Thanks Sheldon. Any BB for a short-lived XTR version is probably expensive beyond the value of a cheap conversion to a nice fixed-gear option.
And I'm interested in the V1 spline specifically b/c I've got a 105 crank with 165mm arms sitting around
So it looks as if the 105 crank with a 109.5mm V1-spline bottom bracket would work, if I went with 40mm chainline (which is where the inner ring would be with a 43.5mm road-double chainline, given that every crank I've measured (from old Sugino that came with 10-speed
bikes to modern FSA designed for use with 10-speed
cassettes, the chainrings are 7mm apart).