are you saying that "initial" is at idle?
Ok yes I see it, at 900rpm.
Are we talking a 340 automatic here? I don't see where you ever said.
Ok then, if it stalls at or near idlespeed; then, that 30* is your biggest problem.
Other problems are; the 3600ft elevation, and the very low 115 psi cylinder pressure. Don't try to overcome the low power at very low-rpm, with tons of timing; it won't work.
By advancing the Idle-Timing so far, you have practically shut off the transfer slots, and that is why you had to crank up the Idle-speed to 900 to keep it running.
Do yourself a favor and back the timing up to about 14/16*, reset the mixture screws to 2.0/2.5 turns out, and set the idle-speed to 700/650 in gear. Now take it for a ride.
The end goal of this exercise is to get the transfer slot exposure underneath the throttle plates to be a lil taller than wide, to set the basic idle fuel delivery, and to just use the mixture screws as idle enrichment-trimmers.. At 3600 ft, it will be easy to run the lowspeed system too rich. If possible, I would try to run the fuel pressure closer to 4.5psi.
And finally, the daymn metering rods have to stay down at idle. And they have to stay down as you drive away at light throttle. To find out when they should begin to open;
Put a vacuum gauge on the intake manifold. Then take the spring right out from under the power-piston. Now take it for a drive. Get her into Second gear, then while monitoring the gauge, do some modest throttle-roll-ons, at various roadspeeds and rpms.. Make a note of the vacuum when the engine lays down. Now put your spring back in, and compare the driving experience. You MOST LIKELY will need a different softer spring and different rods, to compensate for that 3600ft. And don't forget, the darn thing is adjustable for setting the idle fuel....... which has to be done AFTER the transfers are synced up with the timing. And reset nearly every time the Speed screw is tweaked.
Now, if in fact you set the Idle-Timing to 30* with the factory distributor , and the timing is NOT locked out; then your Power-Timing could be 20* or more, higher; Which is a recipe for breaking parts. Your Power-Timing HAS to be limited to, in the range of 32 to 36 degrees, to be "all-in " somewhere between 3000 to 3600. For safety sake; the more you run, the later it should be delayed to.
For a streeter; usually the tires are spinning to 30/40 mph, or more, so, not enough timing is no big deal until then. But for you with only 115 psi CCP, and at 3600ft, I doubt your tires will more than chirp, and if that is the case, then timing will be very important, but not as important, IMO, as getting the power AFR dialed in, cuz at the stock jetting, she will be a lil faaaat.
A FAT engine is a slow slug, that hardly cares about it's timing. But as you lean it out, and the power picks up, you will have to start paying attention to the timing.
You may have to restrict the secondary opening angle
The Vacuum advance system should be defeated until you get the basics dialed in.
With an automatic; from after the idle is set, to until she hits the stall-speed; the engine does not much care about it's timing; so 30* at idle, is an excessive street number. It's NEVER a good idea to force timing on an engine. She'll be happier with 3 degrees not enough than with just one degree too much.
