I agree that the BB is probably Swiss. I'm not sure they ever switched to BSC, but they could have. Don't worry about spindle length for now, the main thing is to get the correct threads. Figure that out first. If the BB shell is Swiss a new bottom bracket will be expensive.

1. Measure shell width first. If it is 68mm not 70 then you know it is British, French or Swiss.

2. Determine if the fixed cup thread is left or right handed. If right handed, it is French. If left handed, proceed to step 3.

3. Try threading in a BSC BB cup into the frame. If it fits properly*, it is BSC. If it doesn't, it's Swiss.

4. Give up and take it to an old timey shop. BB compatibility can be difficult even for pros. Warning, some newer shops are probably not going to be able to tell a Swiss from a BSC BB, since a BSC will fit into Swiss threads IIRC, albeit loosely.

*refer to Sheldon's crib sheet.

Swiss BB options are Phil Wood ($$$), IRD ($$) or whatever old stock you can find.