So...as it turns out, I *didn't* know (or, to be more precise, had *forgotten*) the type of precision needed to use a 1/4" torque wrench. From what I can figure, I'd spent so much time with the 1/2" wrench, I'd forgotten how light of a touch one needs - and the click / stop on the 1/4" is *much* more subtle than the larger ones.
Another two (!) trips to the hardware for bolts, and I figured out that 30mm is the best / optimal size for the throttle body bolts -- M6 x 1.0 x 30mm -- flange bolts.
(this is for the GMT-8xx trucks specifically, and if you use a throttle body spacer, you'll probably want a 40mm or longer bolt)
After thinking about it, I think I'd give serious consideration to getting a 1/4" wrench that has the light / beep notification, since it's super easy to run right past the stopping point on the HF wrench, at least (for whatever reason, it doesn't continue to click / stop, especially if you're not moving it slowly / gently.
(hey, where's that 'garage' / 'tool' section we were all talking about a few weeks ago? LOL)
Decided I'd pry open the covers for the knock sensors in the valley cover, since the rear one especially is prone to collecting water / rusting / failing. It was in pretty good shape - BUT - in prying up the plastic cover, I broke off the plastic lip on the sensor that holds the locking connector in place. Thinking that it was a matter of not having enough slack in the wire that feeds through the plug, I tried creating slack in the front sensor wire / plug. Not moving. Pried up the front connector, even more carefully...and broke the lip on that sensor, too. I have the feeling that +15yrs of a high heat environment made the plastic brittle. But GM makes it pretty impossible, with the depth of that plug, to even see the connector underneath, much less press the ends of the connector to remove it from the sensor w/o breaking it. Or, I'm just not good enough of a mechanic. Probably a bit of both.
So...I get to decide on whether I want to chance the connector slipping off the sensors, if I leave them in place, or purchase replacements for two otherwise working sensors. I can get them for ~ $80 shipped online, but will be waiting another couple of days for them to be delivered. Or, I can spend $150 for the pair, retail (I'd already looked them up beforehand...should've just ordered them, but I knew they were working, so...)
Decisions, decisions...