Adding weld to the rib would produce a banana shaped Brampton part - not recommended. And setting the lower bearing seat higher is a very awkward operation, you have to keep alignment and parallel seats of upper and lower bearing absolutely spot-on - not easy to do.
So really you´d better add some weld to the stops on the head lug, no risk of deformation there, you can use simple arc welding with standard rods. The head lug is most likely low carbon steel casting so no problem with welding added to extend the stops. A few wet rags around and you could do it on the bike. The stops were effective on most Brampton bikes I guess, but just and no great contact face there so some mod is a good idea.
Vic