I'm on the side that felt that the plugs behind the plate were not needed. My cold idle pressure is around 70, warm it will drop to 45 or so in neutral using a high volume pump and 10 w 30 oil. Having the plugs in place probably doesn't hurt but I still don't think they matter much unless you have a thrust plate like this:
View attachment 1991619
That has the end blocked on one side and a diverter on the other. If the pressure in the gallery were to run into the plate and make a 90 degree turn down, it seems like the chain would be drenched in oil. Maybe this was used in conjunction with a blocked passage with a small hole drilled in it to restrict the flow? I never looked into that but it could have been that way.
I used one like this:
View attachment 1991618
Of course I cleaned it up before installing it. I've found that over the 25+ years of the LA engine and 10 or so of the Magnum, there have been a few changes, some obvious and others were subtle. For example....For many years, the cylinder head torque spec was 85 ft lbs but it was later increased to 105. I can only guess that revisions like this were done to address some shortcoming. The various assembly publications vary as far as whether to use block off plugs in the lifter gallery at the front. Some call for it, others don't even mention them.