You do not want to do roller bearings. There is not enough meat in the sector housing and the sector is not hardened for running against rollers. However you do have the "good" 15:1 worm and sector in the 34 box which will transplant into the 32 (13:1). You do want to add a modern seal to the housing for the sector or it will leak forever. As to rebuilders, Richard Lacy of Early V8 Garage in West Covina CA 626-338-2282. He is the master at this and when he finishes with it, it will be perfect or better.
Thanks
Floyd