Macrobb, If I understand how you're describing the fuel rail on this engine having the #7 line or injector fail should not have had any affect on the other 7?

Was I basically fed a line of crap?

With no metal present in the oil and sitting so much in the last 24 months - what are the odds of this being some sticky valve spring (or the like) causing a stuck valve? I know a stuck a leak down test is how I would diagnose a aircraft engine. Air escaping through the carb would be and intake valve, air though the exhaust would be exhaust valve.

I didn't hear any ticking, tapping, banging, scraping, grinding, or any other noises when she stopped - other than the one bang.

 

Yes.
Heck, I've tested this myself once, playing around with an IP on my workbench. Rigged up fuel supply and power and turned it by hand. Hooked up /one/ injector line and injector, and turned it by hand(the part of the rotation where it's compressing the fuel? *much* harder than free-output of the other 7).
I got fuel squirting out of the single injector just fine.

'Course, I've also done it on the truck, generally by accident <_<. It's always fun getting the truck fired up after pulling lines, finding that it's still running on 7 after a few seconds and realizing that you've just sprayed diesel all over everything by doing so. Fun times!

Yeah, you can do that. Obviously, remember to rotate the crank so that the cam isn't holding one of the valves open while doing so...

Honestly? I've got no clue.