Probably the most sure thing here (for me) is the sump must come off and be examined
I cant remember whether the sump can be wiggled out by raising up the engine or the IFS needs to be dropped
Even if it is not caked with sludge, I always find sand in the bottom corners of every sump I clean.
I assume this is casting sand, trapped in the sludge
The way I check, is lick my finger and run it around the cleaned out corners,
dont want freshly liberated silica sand running around bearings, there is always some left when I do this test
I have an early ('51) alloy sump sitting here ready to finish cleaning out and power wash, it has about 1/2" of sludge
If it was all sludgy I would run a couple of oil changes to flush out the oilways
In our Club, we always try and make sure members dont feel tempted to ignore the sludge traps in the crankshaftbif soing a rebuild