I am re-powering my '51 Chevy 3/4T from a 235 to a 261. I plan to use a 261 block and a 235 848 head to gain compression. Since the rocker arm assembly from the 261 is in the best condition, I am planning to use it for the build. I notice that the two end rocker shaft supports from the 261 have a slot milled into the side where the shaft goes through, which I suppose is so the shaft is held securely. Is this correct? What is puzzling is that the 235 rocker shaft supports are all solid with no slot. Does anyone know why they are different? Are both supposed to have the slot and maybe the PO installed the wrong end supports? Any help would be appreciated.

Rocker Shaft Support with slot