Don, thanks for your suggestion, I went to home depot and bought a flare to compression adapter, and compression to pipe adapter. A helpful HD salesman flared and gave me a small piece of 3/8" tubing. With all that, I installed a vacuum gauge that I had.
The good news is that the pump pulls good vacuum. The GAST gauge (pulled from a broken pump a year ago) is very inaccurate, it is not even zeroed, but it shows vacuum in the "neighborhood" of 28 inches. That's good enough for pretty much any application for myself, and likely the pump works close to its spec of 25 microns. Its appearance suggests that it was only lightly used.
The bad news is that the about 1" piece of copper tubing will eventually fail from vibration, as it vibrates somewhat and supports a cross fitting and a vacuum gauge (eventually to be also fitted with a connector to an air tank, a valve, and a connector to whatever is being vacuumed).
I decided to not worry about it too much, when it fails, I will think of something better or may try to use a much shorter piece of copper tubing, or maybe I will mount the gauge and fittings separately using plastic tubing. Whatever. There is no safety issue here.
I decided to take a little risk and try a $18.99, five gallon air tank from Sears. If it collapses, not a big deal -- but I think that a smaller tank is less likely to collapse than a big one.
I will also try to fit a exhaust filter (to capture oil mist), also a pull from a rusted 1/3 HP gast pump. Here, I am just a little worried that a filter made for a 1/3 HP pump, may be in somne ways inadequate for a 1/2 HP pump. Any thoughts on this?
i