340 camshaft question, yea another one.

There are TWO ways to control your idle speed; Throttle opening and timing. But no matter which you use, the engine wants the right amount of fuel.
To illustrate this, I have run engines with empty carb bowls, by spritzing fuel down the barrels and holding the throttle open. I have also started engines with no carb on them at all, again, with a spritzer. If you have ever started a flooded engine by flooring it, you have done a similar trick.
On an idling engine, you can grab the dizzy and pull a lot of timing into it. And the more you give it the higher the rpm climbs,until the engine complains about too much. And you can dial quite a bit out, before you have to compensate with throttle opening, and eventually it will not be enough timing.
Your task is to find the sweet spot. And the starting point is to get the T-port sync right. Once the sync is pretty close, you only have timing and bypass air to work with.
It looks to me, that you know all about this. But it seems the tune is not quite right. Once the Sync is set, you must not vary the rpm much with the curb idle screw. The idle speed must be set with timing and bypass air. Did I just echo that? And I think this is where your tune is failing; well that and the 7* timing drop-out.
So it's unfortunate that the cam is already out