Hey guys, the taper on a Stronglight spindle is significantly different from a modern Campagnolo crank. I've seen too many people say Stronglight is ISO when it's not at all. The Stronglights have a very long tapered section whereas the Campys/ISO are very short. There is a 2-3mm difference in length of taper. Don't try to use your existing spindle with the Campy cranks. At best it won't work, at worst, you'll munge the crank.

Stronglight/TA taper is closest to JIS which is probably why the SR cranks worked out OK. To put a modern Campy crank on an old set of French or Swiss Stronglight cups, you need a later Campagnolo spindle made for the later thin cups. You also need the exact right length, but the good news is that French/Swiss BBs are 68mm, just like English, so you don't need a French/Swiss spindle. Just get a later Campy one in the right length, use your existing cups, new grade 25 bearings and roll along on your way.

Karl