Sounds horrible. Sorry such a painful experience. Cannot expect an engine builder to be an engine compartment restoration person also, but there are many things in the short amount of the video that I watched that show the obvious lack of attention to detail. I'd submit that a local engine shop is not going to have every chassis manual for every vehicle on the planet in that type of business - but they SHOULD keep track of nuts and bolts and where the hoses were removed from so they can replace them. Did you pay for a long block rebuild on each or did you pay for an engine resto and to get it running great/tuned, etc? I ask because there is a fine line between the two. The latter is what it sounds like you were after - but if you paid for a long block build only, then they will stuff a decrepit carb right back on there and leave it to the customer to sort out all those "nit noids"... Has happened to me too, with a body shop though, pointed out some clear lies they had told me on the phone when I went in to check on it, ended up getting in the car and driving off with masking paper still on it, after a few words I probably shouldn't have said. But, being 18 and broke at the time, perhaps I was expecting a little too much from the local Maaco...
(Still, didn't expect the outright deception I experienced with that particular one). I'm sure they aren't all that way. But that was a long long time ago.
While you didn't mention it above - if the name of the place appears or is implied in your video, be cautious or you'll have a lawsuit on your hands and this nightmare won't end. It's not worth it.
What happened when you returned to the builder and discussed all this with him?