> needs the little Crane cam/stop plate in the vacuum advance
Oh, bosh. Don't bother.
This is basically a stock-like engine, right? No oversize valves, HI-lift cam (one model up from stock isn't much difference), or 6-73 blower? Cadillac didn't leave much on the table when it came to little stuff like timing advance. Timing is not too critical, and getting it well into the happy zone was a zero-cost win-win for Cadillac. (Go to the first Falcons for terrible timing control, as bad as the first V-8s.)
Static sets the idle advance.
When you crack the throttle to 1/10th, vacuum is applied to the advance. This gives you a little goose as you come off idle. It also sets the advance for good economy at small throttle openings.
Vacuum advance is nice in a stick, to give you a little grunt as the clutch engages. But you got a 500 with a slushbox. You have grunt and don't need it to get rolling.
Small-throttle cruise _is_ important on a 500 _if_ you are going to do 50,000 miles anytime soon. A 5% difference in economy eventually becomes a lot of dollars. However I suspect this isn't your 100-mile-a-day commuter car. That you will do 1,000 miles a year. The difference in annual gas cost won't buy a nice birthday cake. Anyway you can set a good-enough small-throttle advance.
Prop the throttle so the vacuum advance pulls to its stock stop. Turn the distributor to get the specified static+vacuum advance degrees. Now close throttle and see where the static falls. If anywhere near 20 degrees, and if the idle is good (it isn't fussy though you may want to trim the throttle idle-screw), it's good to go.
For your uses, the centrifugal advance is more important. A 500cid isn't there to run 1/10th throttle. When you NAIL the pedal, the engine should pull, but I'm sure it does. If it pings at low RPM, take off some static.... but really a 500 in a medium chassis won't stay at low-RPM for long. RPM will rise. At higher RPM you have more turbulence in less time, pinging would be less, so centrifugal weights bring in more advance to keep and raise the torque. If they come in too fast, it pings; too slow, you don't have all the torque you wrestled in there. I'd be most concerned about pinging. (Gas ain't what it used to be.) If it pings, try taking a little more static off, try one jet richer; but you may have to change springs/weights (stronger/lighter).
