Thanks for pointing that out, it's more or less so you can rest easy on the other stuff and then replace the seals because you know the are bad. Also, you can use the air to hold the valves closed when you do it. On the cylinders too difficult to get an air hose to, use the rope trick. If it runs good except for the puff at startup and you don't intend on tearing it down for more work, it isn't necessary to worry about everything. Just drive it after replacing the seals. Make sure any cylinders having oil on the plugs don't have wobbly loose valve stems. Seals won't help that.
It's not a matter of a leakdown test is "better" than a cranking compression test...they verify different things. They're complimentary. The "Three Sisters" of cylinder diagnostics are the cranking compression test, the leakdown test, and the cylinder balance test. They're not the "only" cylinder diagnostic tests, but they're all fairly simple, fairly quick, the equipment is not overly expensive, and together they test for a wide range of problems. Of course, not much is more simple than running the engine with a vacuum gauge connected to manifold vacuum; and there are some times when a running compression test is worthwhile. Lots of folks don't know that a running compression test is even possible. Specialized tools can be used...if you have them. An ignition oscilloscope is fun to use, as is an exhaust-gas analyzer. 180-ish psi compression for a '72 is not just good, it's fabulous. Maybe too good to be true. I'd be checking the compression tester for accuracy. The simplest way is to connect it to "shop air" and compare the compression gauge to the regulator gauge on the air supply.
I agree Schurkey, I bought the compression gauge at Pep Boys and it's a Actron, the fittings are steel not aluminum which I liked. I read a few good reviews about them but you know how that is so I'll be checking it when I get the chance.
