I would look at the 9.3 x 64 as this will take less work than the 9.3 x 62 would, but the bolt face would still need to be welded to the smaller base diameter.. Any of the cases based on the 404 Jeffrey including the parent case would take minimal work except the action will need to be opened up and the bolt stop set back for the full length 404. Any of the short (medium) belted magnums will work but the barrel will need to be set back so much you will have a big gap to deal with, better to get a new barrel. If you have the components already a 9.3 x 330 Dakota would be an interesting one.
One I would consider is a WSM on a fast twist barrel like a 1-7". In 6.5 or 270 this would be sort of like a 6.5 x 284 but pumped up a little bit in velocity. In the 76 action you could seat bullets as far out as they will go with the short case. I would use and shoot this more than a medium bore.
