B posts on 403

[mikebro]

My 403 was "restored" sometime in the 70's. The bottom of the B posts (ie the steel uprights at the rear of each door, had the (corroded) aluminium of the body skin covered over with a piece of galvanised sheet steel for about the bottom 6 inches. This had been rivetted to what was left of the aluminium and then filled over with body filler. I have pulled all this off and am in process of welding new steel in behind the bodywork. There is enough steel left for me to see the shape of everything so the actual B posts will be accurately repaired. Then I will be cutting new aluminium sheet pieces which I will braze onto the (cut back) bodywork. Since the bottoms of the aluminium bodywork were completely corroded, my question is: was the aluminium originally crimped over the bottom of the B post, or was it rivetted to it? I can see it was crimped over the front edge of the B post but cannot tell how it was fixed at the bottom.