can an SWB oil cooler leak be fixed ?
 

My '66 911 factory Behr oil cooler sprung a leak. Lek appears to be from the fin section. . Can these be repaired ? If so, then by whom ?

They can but they often leak again in a different spot.

A radiator shop can assess it. Pacific Oil Coolers does a really nice job of cleaning and repair.
However, in the long run, you will likely be better off to just pick up a new oil cooler.

A 66 is getting a little long in the tooth, corrosion and vibration..
 

I'd suggest sending it to Pacific oil cooler for an evaluation, maybe the heat cycling/vibration haven't rendered it a poor candidate for rehab.
Give them a call for an estimate to do it - might make economical sense, given the cost of new.
They have a solid rep here and the ferrarichat forum. The fact that they do aircraft heat exchangers is significant, as well.
My .01 cent
Chris