Is 129mm the length of the original cup-and-cone spindle? Often those older spindles were asymetrical (the drive-side stuck out a bit further).

If this is the case, a slightly longer--but symmetrical--cartridge bottom bracket may be what you want (the drive-side would be the same length, but the non-drive side would stick out a bit further than originally).

I would compare how far the drive-side spindle sticks out past the cup on both the original and a new bottom bracket--and match them up.

This link may help: http://sheldonbrown.com/bbsize.html

If the above is not the case, sorry for the unnecessary info....