390 valve adjuster wearing out

I have a 1968 Century resorter boat with a newly re-built FE 390. I purchased the rig just after the re-build so I don't have all of the specifics of what was done. The number 5 cylinder keeps wearing out one of the valve clearance adjusters (the one closest to the end of the block). This is a solid lifter engine. I have replaced the rod and the adjuster and the same thing keeps occuring. I run the thing for 3 or 4 hours and pull the valve cover to discover that the tip of the adjuster that sits in the cup at the end of the rod is worn down at least 1/32" to 1/16". I've checked the oil path and all the holes are clear. I'm adjusting clearance to .025" before I run the engine.

Do I have a warped rocker shaft? The engine overheated once when the water pump failed but I caught the problem early so it didn't get too hot.

Could this be over-worn rockers that let oil leak out before it gets to the adjuster?

My oil pressure is about 82 psi at 2500 rpm warmed up and about 72 at warm idle.

I have ordered two new rocker arm/shaft assemblies with solid spacers.

Does anyone know if I'm chasing the problem correctly?

You should use a drill and buy an pre oil rod that sticks down where the distributor gear goes and put the drill in reverse (counter clockwise) and let her rip. See if you have oil coming out of that rocker tip or not. Secondly, make sure you are using an assembly grease on that part prior to start up which should aid in it's break in. I would suspect that you're not getting oil there or it was too late because no grease was used.

Where can I get pre-oil rod?

I'll bet ya a beer that it ain't oiling that peticular push rod, I worked on a Mopar 318 once that had a piece of metal flash in the oil feed hole in one of the lifter bores.....