So, I keep going on forums, asking the same questions I feel like, but I just want to make sure I am making the right decision before I dive into anything.
1996 12 valve 5 spd, 325K miles (got sold to me saying it had 25K on the rebuild, love being lied to).

I had some sludge looking stuff in the oil, took a sample, sent it in and got results of high potassium and sodium and some copper also (sample document attached). After the results, I changed the oil and filter. Obviously, this would mean some coolant in the oil, but here is my dilemma. The amount of coolant I have lost is very very little. I drove it about 60 miles after the oil change the other day and lost either no coolant or like 1/4" depth on the coolant overflow bottle (I didn't mark a line, but I filled the bottle to full and after driving, it was still at full). I drove it 600 miles before the test and maybe lost a pint of coolant...also with a leaking heater hose, so that contributed too. There is no crap on the dipstick, just oil. Pulled the valve covers, just plain oil in there too. The only place I can find anything that points to an oil and coolant mixture is in the oil fill tube (see picture attached) and it looks pretty nasty. No oil in coolant/radiator either.

I am confused and asking for help because I don't want to tear this engine up, and I obviously have coolant in the oil (from the test), but everything I have researched has said/showed a large amount of coolant loss (gallons) and a yellow cake batter colored liquid everywhere (dipstick, valve covers, etc.). I am trying to avoid spending a lot of money to "fix" a problem that isn't there.

I need opinions on what you all would do if you were in my shoes, thanks

Could it be old residual before someone supposedly changed hg/rebuilt, maybe didn't get flushed very well. Or could be oil cooler leaking. Compression test maybe, Leak down?  

Pressure test the cooling system 

Warm up the truck in the evening and park it in the shop if available. Then drop the oil plug and the oil filter and let it drain all night long. This will get a majority of the mess out  of the crankcase. @Dieselfuture is right it could be a bad oil cooler. 

 

Others cracked head, bad head gasket are possible. Mine when the head gasket start to fail it leaked externally. Rear right of the down the back of the block. I had head curl. I also had back valve guides and bad valve seal excess oil smoke at start up. Cost about $2,000 to do head studs, gasket kit, and the machine work for the head and valves.

Thanks for the info, I am going to pressure test the cooling system today.