Larry, from the picture, you have an 848 head on the motor. Those 848 heads entered production for the 56 model year and were found on 56 to 63 passenger car motors. I am not sure about the truck motors. They could also be found on Canadian Pontiac passenger car motors (261 blocks with the 848 head. Those heads had steam holes drilled in them for the 261 block Siamese cylinder bores). There were two eras for the 848 heads, the 56-58, and the 59-63. 59 is when gm Made it’s final design change to the oiling system of the motor. So for 59, the factory got rid of the steel line behind the side plate that fed the rockers from the rear cam bearing, and instead feed the rockers from a drilled passage direct from the oil galley, enlarged the oil feed oraface to the rockers, used a pinched off oil connector and created a sort of pressurized oil system. To make sure this pressurized oil dribbled out of the dribble holes for the rocker arms, as opposed to spitting over the arms and not oiling anything, gm moved the oil groove inside the rocker from directly intersecting the dribble hole to being off set.
So, if that head is a 56-58 casting date, and you can confirm that the rocker arms have the inner groove intersecting the dribble hole, you want the oil connector that is not pinched off but looped around. If you discover the Head is a 59-63 and the groove in the rocker is offset from the dribble hole, you would want to use the pinched off 59 and up oil connector.
That being said, lots and lots of the 55-58 oil connectors were pinched off when the rear cam bearing got worn and lost a little pressure, or the steel line got a little clogged, to help keep a little pressure inrocker shafts to get oil to the rockers, especially the end rockers. So if you use the looped version and find no or insufficient oil coming out of the rockers, especially Nos. 1 and 6, you might pinch the loop closed and see if that helps.
