I have a 48 degree R-3 block motor that is finally seeing some use and miles.
It runs great , pulls like a draft horse and stays at or below 180 degrees.
Charlie's 6 qt. pan and 3 qt. accusump , Melling HV pump.
Solid roller with push rod oiling.
.040 restrictors in the push rods.
The oil pressure drops off once it is warm..........15 lbs. at idle........950 r.p.m.
It pops up to 40 as the revs come up to 3000 and will max out around 60 p.s.i. at 5000 and above.
But seeing it that low is not comforting.
Brad Penn 10w40.
I went with the accusump because I felt I might have drain back issues from the top end and though it would be good insurance.
In the motor , I ground the pipe boss / drain backs in the valley flush and added a 1/2 " hole at the rear of the valley that drains right on the cam gear / oil pump drive.
I am afraid that it might be because volume in the pan is low after driving it around and the oil is being stored in the heads.
I do have a vacuum pump and after a 30 mile trip last week , all I got from the tank was what appeared to be trace condensation residue......not even an ounce , and more water than oil.
I am also wondering if the lifters may be uncovering the oil feeds maybe ?
They are not bushed.
I used the MoPar tool and drilled .090 feeds in the lifter bores.
G.S. / Crane Ultra Pro's and not crazy lift......like .668
And maybe I am worrying needlessly.
But I am still worrying.
Anyone ?
I should add.......Auto Meter Pro-Comp mechanical gauge

What are the rod are main clearances

I don't recall the exact numbers , because it was assembled four or so years ago , but they were on the loose side..........0025 and .0035 ish. if memory serves.
I know it is written down somewhere , but that is going to be pretty close.
Side clearance was in the .015 neighborhood.

3/4 groove main bearings also.

My old BB pump gas 400 stroker motor (4.300 stroke)had oil pressure similar to yours with 5W20Wt oil hot(above 160 F), no issues ever except when I let the oil level get down to 5 quarts in a stock Mopar 6 quart 1970/1971 Hemi/440 six pack oil pan It would loose a little oil pressure at the end of a 1/4 mile run when I let off the throttle with the oil level low, never did that with more oil in it above the add line on the oil level dip stick
Full groove main bearings and a lot more oil clearances than yours with no bushings in the lifters with 3 different brands of solid roller lifters in that motor.
I like to use the old rule of 10 lbs. of oil pressure per 1000 RPM, ie 70 lbs. at 7000 RPM
Me thinks your good on using that pressure with hot oil

I have the same low pressure issue and I think it's related to the lifter's oil bands being located too high and bleeding oilpressure out the top of the bores (Flattappet hydr. cam converted to solid).
But I used bigblock lifters in a 360ci engine, so that might be the main reason.
The issue starts after startup just when some heat gets into the oil.
Will be upgrading to a hydr. roller soon.

I tapped the holes in the lifter bores & installed 0.35 brass restrictors in my old r3. Dont remember the size of the pushrod hole size which really didn't matter. I also drilled 3 5/8" holes in the valley for drain back which worked out perfectly. I had my engine ideling around 1500. Pressure was around 35 in gear.