Looks very very good Scott! You are definitely going to accomplish that look that you are going for. You should hire a local photographer to snap some pics when you are done. Post them on instagram and break the internet.
I recommend doing that before you take it to the track.
I kind of skimmed through the video but some thoughts:
* The 1974 had a black-slat kidney. The all aluminum grille will look really sharp if you want to keep it. If not, you can actually remove the slats and paint them or anodize them black. A black candy paint would look nice. Personally I would leave it all aluminum as the contrast really pops
* I'd stop stressing about the bumper. There is no "proper" way to mount an early bumper on a 1974, as the whole job is custom. Even if it was removable you probably wouldn't do it more than once. Just like coilovers, the idea of adjustability is really just an idea. Reality is set-it-and-forget-it.
* Where did the holes for your side mirrors go?
* The width of your dash wood looks about right to me in this video
* Do you have license plate lights that fit into the bumpers
* When you spray the seats you should consider removing the chrome side pieces. You may want to just tape off the aluminum back trim as it is a pain to remove. AFAIK it is riveted in place.