360 Questions.. pardon my ignorance.

So with the vacuum can disconnected I settled at 10 degrees initial, it’s a bit back from rough running and a bit higher than sounding lazy. Idle is stuck around 500-550rpm, mix screws are 2 turns out and I had to put a turn and a half into the idle speed screw. Vacuum on the gauge has a little bounce to it but not dramatic, shows to be in a good range. RPM only drops 100-125rpm when put into gear.

Here’s the issue I’m on now.. when I bring the vacuum can back in I’m at almost 50 degrees of advance at about 750rpm. It is firm going into gear but I wouldn’t say it’s slamming gears.

I measured the spark port on the carb, it show vacuum all the time, increasing with engine speed. The only other ports are on the firewall side, one for PCV and one that I believe is the heated air hookup for the air filter. Which leads me to, I’m sure, a wildly incorrect train of thought..

With those variables could I not set the motor back to TDC timing like the shop manual states and rely on the vacuum can to apply the timing? That appears to be how it would have been originally setup?