Ideas on what's causing my click/tick/rattle noise?

well, I did just go back and re read from post #1.
I have to add... My Dad had a /6 in an 82 Gran Fury in the late 80s. I took the car one day, and noticed the water pump sounded loud/ and I told him about it... and he said "we'll wait til it gets worse, it isn't losing any antifreeze"
the next time I used Dad's car, (like a week later, he'd driven it daily in between) the water pump totally went out, bearing came apart.... were talking "fan into radiator" bad. I limped it back home, it had gotten HOT. I'd let it cool a while, then start it up, get to cruising speed, shut down, throw into neutral, shut off key, and coast as far as I could, repeat. The result ended up with a cracked head. To get his car going as quickly as possible, (and knowing alot less about these engines then, than I do now/ not saying that I know much now) I took the head off my 80 Aspen that was recently wrecked. 700 miles on a fresh overhaul on the Aspen's engine. (which was a much earlier slant, earlier enough to have had drool tubes) I put that drool tube head on the 82 engine, and everything worked fine. and I remember having to drill out that rocker shaft, for the fatter rearmost bolt that the drool tube head had on it. but he drove that car a few more years like that, ran fine without any problems from the engine. that Aspen's engine, had been my 1st slant 6 overhaul. story on that one for later. I'll just say for now, that's the car that I learned about there having been 2 different sized torque converter registers, over the years. gives you an idea how much older the engine I rebuilt for that car was, than the car itself.

and pic in post 129 answers a question I saw posted much earlier in the thread, about exhaust valve rotators. the engine taht is the subject of this thread, doesn't have them./
but I know that they did use them, on some slants. I bought a freshly rebuilt head a year ago from a guy on CL, a guy that used to run 2 charter fishing boats on Lake Michigan/ each powered by twin slants. He kept a fresh head ready all the time, as he complained about what unleaded fuel had done to the heads on his engines.
In the box of extra/spare parts that came with, (several old valves still in serviceable condition, springs, extra rockers, drool tubes, and more random, slant specific goodies) were several shorter valve springs and a bunch of valve rotators.....I kept some but picked thru the box, and scrapped a good percentage of it.