Running great one day and next it stalls every time I hit the gas too hard

I went through it all again tonight. Warmed it up and checked timing (14 degrees at idle), vacuum (14inches at idle), looked for fuel dribbling (none), accelerator pump shot (nice clean spray of fuel), no vacuum leaks, no shorts that I could see. No hesitation or stalling when I was hitting the gas in park so I decided to bump up the timing a little to 18 degrees (plugs were slightly black @ 14 degrees) and took it for a spin. Now it didn't stall when I whacked the gas, just a small stumble.

So do you think I'm on to something with the timing or should I keep focus on the carburetor? I did notice a little dried gas right around the base plate to the body of the carb. Maybe it's time for a rebuild. After all my cousin probably ran it for 10 years, then it sat for another 15 until I got it from him. I just plunked it on and set it up. I don't think it's ever been rebuilt.
Yep, go through it.
Black is obviously rich..
... and at 14 initial with the idle mix correct.. 'even if not optimal timing'.. the plugs shouldn't be black.
So you're fouling plugs- its rich
It also seems to like more initial timing, good. You're onto something.