Hughes AirGaps have been on backorder for about as long as I can remember. If I remember it right, they aren't exactly a bolt-and-go part either, something about getting the fuel rails and throttle body stuff to fit right is finicky. Could be wrong though, it's been a while since I read into it.
The M1 2-barrels are our engine's unicorn. I've looked around off and on for years and only ever saw one for auction. It ended up going for somewhere around $750 and I think it needed a bit of TLC.
For all practical purposes, unless you want to do a carb swap, the factory kegger is all you're gonna get. Plenty of people have done plenty of stuff to it and the end result is the same: it's a truck manifold meant to churn out plenty of torque at low RPM and that's that. It simply doesn't respond well to modifications meant to push the powerband to higher RPM. Shortening the intake runners COULD give a slight increase to mid-range power via manipulating Helmholtz resonance, or some such thing, but I've yet to see a before-after dyno chart on this. The best I've come across is "butt dyno" feel, which I suspect is more placebo than anything (perhaps the new pan gasket you installed in place of the old, toasted one while doing the job had more to do with the engine running stronger than before vs the manifold modification?).
Also, if anything that I mentioned was brought up in the video, I apologize. Can't be bothered to create an account to watch it at the moment, LOL.