How much "shake" at idle is acceptable?

So your 340 is injected?

If it had a carb I could make it idle at 550 no problem.
With a manual trans , you sorta got to get the idle down, so you can drive slowly. 1100 rpm with 3.23s and a 2.66 low is 10.2mph, Which sucks, cuz you gotta slip the clutch a long ways out.
An idle of 550 would cut your minimum speed in half.
But I guarantee that you cannot make it idle at 550, and still drive it, with hi-stall timing, because it will get to bucking like a wild horse. You would need to get the timing down to ~5*, to kill the low-rpm power.

On another note; is that cam a solid-lifter cam? Or why is it so noisy.
If yes it is, I would recheck the lash, on account of maybe a couple of valves are too tight.
You might be able to get a better handle on her, by doing a compression test.
A 262 advertised cam is pretty tame, smaller even than the factory cam and with about the same overlap. The factory 340s idled on 5* just fine.