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The original BB being asymmetric does complicate things.
The DS was 30mm, so in theory a symmetrical BB would be 114mm for a 43.5mm chainline (between the chainrings).
So 111mm should be close if you were to put the ring on the inside: is that possible with these cranks?
If you do need 109mm then I think Victory or Triomphe also used that, although they aren't much easier to find than Pista.
I'd be tempted to use a 107mm UN55.
Scilly.Suffolk-
The inner ring on these cranks mounts onto the outer ring using separate bolts and spacer rings, and therefore there's no 'inner' position on the crankset. You've also got the problem that the chainring mounting bolts sit about 1mm inwards of the spider, as they're not recessed.
Whilst I don't really want to use a JIS BB, it does sound like your suggestion of using a 107mm UN55 might be a good one. I'll still have a go with the Campag 111mm one first (when my Campag cartridge BB installation tool comes in the post).
Thanks again for your help and suggestions.
Rhodrich
Thank you for those links. Very informative! Not sure I've got the answer though!
I have a mid 90's cartridge bottom bracket that's 111mm that looks like this in my bike cave:
I'll give that a go, and see how that goes. I've got a feeling the chainline will still be too far out though. If that doesn't work, a 109mm Pista BB might have to be purchased (if I can even find one at a reasonable price!), but I've got a feeling that even if that works, I may have to clearance the RHS chainstay slightly (using the hammer/broom handle technique) to prevent the chainring fixing nuts from fouling.