The casting number is indicative of a 261 head. Casting date looks like 62. Block looks like 61. So here is the deal with the rockers. 55-58 motors used a slightly different oil system and thus used a slightly different rocker arm. If you pull a rocker arm off one of these motors and look inside, you will see a groove that directly intersects the dribble hole. In 59, the oiling system changed a little and became sort of a pressurized system with some volume and pressure improvements. One of those changes was that the rocker arm assembly connector was now pinched off as opposed to the open end loop style of the 55-58. Also, if you look at a 59-63 rocker arm, the groove is now offset from the dribble hole to keep the rockers from spitting over the rocker arm and coil spring with the higher pressure. So given a 61 block and a 62 head, you would use a pinched off connector and offset grove rocker arms. The connector on your motor has been messed with and looks to be an earlier style connector that had the loop cut off and then cracked when the installer tried to make the lower part of the tube fit the head. You could clear off the jb weld and have someone braze it closed (the damage). And I would probably clean up the other end and crimp tight. That or source a proper replacement.
Also, if you look closely, you can see the connector is missing one of the spacers that keeps the spring in place. Replacements can sometimes be hard to come by so a good alternative is a valve spring shim. One other thing, and without having the rockers in front of me, at least one has been damaged a little, and a few look like someone may have enlarged the spit holes, at least on some of the rockers. If that turns out to be the case (and I cant really tell for certain looking at the photo so if you could use a drill bit and see if you can suss out what size the holes are and if they are all the same size, I can dig out one of my rocker sets and compare), you might consider getting another set of rockers. New Sealed Power units for 59 and up still turn up here and there. Otherwise, get a used set (make sure its complete) and send them to Rocker Arms Unlimited in California. They are the best in the biz and will rebuild them to perfection.
As an aside, that valve cover is the one year only 54 cover with the four vent slots. The slots were eliminated in 55.
