Hard start bad idle

1970 base Cougar 351 Cleveland.

Car had been dormant for a long time. When started carb was leaking everywhere. Put on new Edelbrock 600 and seemed to run fine.

After running it for about a total of an hour it was having trouble idling. Would rev up good but would hardly stay running aat idle. After checking seemed to have an intake vacuum leak.

Replace intake with Edelbrock performer and put the new Edelbrock 600 on top

Started it and it purred like a kitten. Problem solve. Right? NO!!!

Took it for test drive and it drove and idled great for about 30 miles. Then it decided to not idle again. Stalling whenever you came of the gas pedal. As long as you kept it revving it would run

Left it over night and started in morning. It would fire but then die.

Spayed for possible vacuum leak but found none.

It would still rev up fine
Checked timing was set at about 12 degrees

Car still has old electronic distributor.

Could it be the electronic distributor??

I think I have done everything to eliminate fuel/air problem

Any ideas would be appreciated.

Bad gas is my first thought. Have you drained it?

I think you are right on track.

I opened up carb and found about 1/4 inch of greasy gel like muck in the bottom of the bowls.

Don’t know if it was from bad gas or if someone put some additive in the tank then parked it without it mixing in.
Have to drop the tank and look in it