Here's a set of HDC rocker blocks and arms for my '56 heads. HDC has been making these for at least 20+ years. Installed the rocker arm will slowly drop on it's own weight. No way would those '48 arms (shown below) do that.
Problem was that the flexloc nuts Accurate sent with the heads are too wide for one post of the rocker blocks. You have to grind away some material or find 7/16 or smaller facet nuts.
Here's a set of -50 heads Lakeside Bill built for me in 1988. Intake blocks are -48, exhaust block is aftermarket HDC. Check the nuts, one set has 7/16 hexes, the other 1/2" ! Old Bill was trying to do everybody a favor and build them cheap. He helped alot of people get started with the hobby. Actually both style of nuts allow you to use a regular socket to tighten them. We tighten them to 15 ft. lbs. Clymers book says 18-20 ft. lbs. H-D doesn't specify a torque spec that I know of.
You don't need the intake oilers with lead-free valeves and seats.
The intake (-48) rocker arm was stiff at about mid-swing, even so, I put at least 23,000 miles on these heads without a problem. Rarely would my solid lifter pushrods need adjustment. I checked them every oil change.
This is a factory installed felt. It looks like two compression divots near the center of each felt. Wonder how they did that?
Here's new felts installed. First I traced the outline and inlines of the felt , removed the felt and applied a line of 3M Super Weatherstripping adhesive #08008 to both the back of the felt and the cover, comes in black too, instead of yellow. NAPA had it.