So now it seems my options are:
1. use the old cup/cone BB, which will put the rings outboard of their proper position by several mm, as I'm not using the guard.
2. try to find an ISO cartridge unit that's 118 or close. 115 is the best I've been able to locate so far. (Miche, C. Veloce)
3. use a 115 JIS taper cartridge unit, which would put the crank arm very close to the 118mm ISO mark. The benefit of this option is I already have the BB unit. Plus, the crankset is currently mounted on a JIS spindle, so I might do better to leave it that way than to go back to ISO(?)
Thanks for the help.