Any ideas on installing something like this in an Aztec?

I would start with research in an Aztec Parts book and see if something similar
was an option. I serviced oxygen on an Aztec recently. I remember the
servicing port being on the right side aft of the rear window and before the
horizontal stab. The gauge was in the overhead above the rear baggage area. I
would think most of the parts would be available from salvage yards or readily
manufactured like the lines. If you are going to do this it would be simpler
from an approval standpoint to duplicate the Piper installation for everything
including mounting the oxygen tank.

The hardest part will probably be approval. I would talk to the IA who will
approve the installation and get his take on it first. Depending on the
cooperativeness of the local FSDO it could be really simple or a long drawn out
affair. Using all Piper parts and manuals will be easier since that
installation is already approved on Aztecs. There may be an STC as well for
such an installation but that might mean purchasing a new bottle etc.

If the problem is really getting connected to your bottle maybe purchasing the
appropriate fitting would be a good compromise. In my experience most oxygen
service regulators use a hose with a #4 B nut with a 37 degree flare. There
seem to be three different sizes of service fitting. One takes a 7/16" wrench
(most jets) and another a 3/4" wrench (most Mooneys plus IAI jets). The last
type is for connecting directly to the bottle and takes at least a 1" wrench.
This last fitting takes a flareless to flare adapter in order to attach the
fitting to the hose on the service cart.

John Dupre'