Tune-up parts and technique suggestions are in
this thread, with a link to the
valve adjustment article. I agree with the others; a valve adjustment is your step № 1 here.
There is no EGR valve on a '72, the first year for the EGR valve was '73. California-spec '72s got a severely nasty no-valve EGR "system" involving a hole in the floor of the intake manifold that allows exhaust to flow (full time, always) into the intake tract. The list of badness this causes is long: rough idle (necessitating very high idle speed to stay running without shaking you off the seat or stalling), poor driveability and performance, lousy fuel economy. Swapping on an intake manifold not equipped with the '72-only "floor jet" screwed into the intake floor (or installing a a solid plug in place of the floor jet) would be a very fine idea.
Update: Watching your vid, I hear what sounds like an underhood exhaust leak. Likely one or more blown exhaust manifold gaskets. Your '72 exhaust manifold has
three gaskets: one seals the intake and exhaust manifolds to the head, one seals the intake manifold to the exhaust manifold, and one seals the choke thermostat cup to the exhaust manifold. That last one is no longer available; see
here. For the others, it is very much worth your while to get the
good gaskets for the manifolds-to-head and intake-to-exhaust junctions.
Faulty brake booster or booster check valve is certainly worth checking for, since it will essentially kill (lean out) cylinder № 6.
Eventually you'll probably want to do the
Fuel line mod and the
HEI upgrade , and you may also want to take a look at
this post.
