Knocking after shut off

[Taylorjean]

99. Ohv manual transmission. Sat for a decade in garage and less than 200 miles since he's been back on the road. I'm being over the top careful with him until I've got some more miles on him. When I say knock, I mean knock, not a ping or a ticking. Like knocking on a wall with yiur knuckes. A few seconds apart, started immediately after cutting engine and died down gradually over a minute or two. I didn't get the hood popped, but it didn't sound like anything was cranking. I only heard knocking. Only did it once so far. It's cold! Warmer when it did it this morning than the last couple days. It was 13F this morning. I had the heat turned all the way up and drove 20 mins up to 50 mph for part of that. Heat was running when I cut the engine. Maybe related, or maybe it's just the gauge. Heat gauge, every now and then, drops slowly down toward the cold line, but doesn't hit it, then goes back up. Few days ago, I drove 45 mins out and 45 mins back, it was low 30's and the gauge was doing the opposite. Today, it didn't go up, only down and today was when the knocking happened. Haven't tried to bleed air from the cooling system yet because, frankly, it's too cold out. Other things in case in helps. He does have a bit of a misfire, still after I did the plugs and wires. He also has a whine and a fairly small leak in the valve cover gasket that I'll get to when it's warmer. He thew p0171. I changed the fuel filter(thought after sitting a decade it might be full of rust) and it hasn't come back...yet. drove 90 miles since. Oh, and it has leprechauns. Had the cargo and dash lights turned off. It was dark out, so I turned it on and the dash stayed dark. 5 mins later, while I was driving, I switched from defrost to heat and 1/4 of the dash came on. Turned the heater setting again and another 1/4 of the dash came on. Never got the whole thing on , but at least I could see my speed. In case any of that has diagnostic value to the knocking.