Halfafish,, in the very first post you mention that the truck is an 82 D150, later in the same post you mention lashing the valves.
An 82 D150 would have hydraulic lifters.
Did you have the OE hydraulic cam reground with a mechanical cam profile and then substitute in mechanical rockers using the 82 hydraulic head?
Also did you put the mechanical rockers on the hydraulic rocker arm shaft?
Asking as the slant six hydraulic cam has a full 360 degree oil grove on the rear journal and it supplies a lot of oil to the rocker shaft, a good amount of that oil goes down the push rods to keep the hydraulic lifters pumped up.
The slant mechanical cam has only a through hole on the rear journal and puts much less oil up top.
Full time oiling intended for hydraulic head, that is not diverting oil to the lifters will way overwhelm umbrellas seals and even positive valve seals. It will also bleed oil away from the bottom end of the motor.
This may also be the source of your rod bearing issue.
Folks that run slants with mechanical valve trains on reground hydraulic cam cores restrict the oil going to the rocker shaft.
