With engine hot, I could see & aspirate coolant from cylinder 3. Removed head & inspected cylinder 3 sleeve for cracks, but couldn't find any. Inspected head gasket, but couldn't see any failures. Perimeter of #3 piston was cleaner than the other pistons & exhaust valves were brown, as opposed to grey on the other 4 cylinders. Cylinder 4 had more "crud" on it than the others. If there was a defect in the #3 sleeve, would be it be obvious with a magnifying glass? Would it be between the cylinders where block casting is thinner? I'm going to have the head examined at machine shop & any valves repaired, they should check for any cracks. Why would cylinder #4 look worse than the others? Thanks.
Marlin

20 new valves & seals, flatten warped head. $492. Parts arrive from FCP today & I'm ready to re-assemble. $1430 total. Also replacing radiator, hoses, PCV system.

I’m replacing hoses but don’t find (at FCP) the short hoses that connect the banjo fittings from drivers-side head to passenger-side intake & thermostat housing to passenger-side intake. Is there anything special about these or just use pressurized fuel line hose? The driver’s side one is U-shaped & looks like it would crimp. Thanks.
Marlin

I once replaced a vacuum line, pre bent 180 degrees, with a longer section of line that I made into a spiral. 360 + 180, without any kinks. Of course, I used silicone hosing which made it much easier to bend.
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Keeping it running is better than buying new

Cylinder 3 being 'clean' is a result of coolant. #4 being dirty is a result of compression loss. Have you used a metal straight edge and feeler gauge to check the head and block for warps? The small gap between #3 and #4 should be checked twice, that is a known 'hot' spot.

A machine shop may need to replace the valves on #4. At any rate, replace the valve guides on all 20 valves.
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Keeping it running is better than buying new

Using laquer thinner on rag to clean block surface. Some of the discoloration appears to be staining, not debris on surface. I can’t budge it with bamboo chopstick (I used this to clean sealant from cam cover on 960). Do I need to use another method, or is this adequate?

"Staining" can only happen to aluminum because of excess heat. Check that portion for level. If level, ignore it, it may have been caused by the gasket deteriorating and allowing cylinder heat to pass through.

Be careful with the chopsticks. Square ended ones are best!
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Keeping it running is better than buying new

That probably explains why the darkest discoloration was on either side of cylinder #4. I was convinced that there was a crack in a sleeve, but it's looking more & more like it was a head gasket problem.