Hi All, I can't get into my B Body Forum right now but this problem should be the same for all Mopars.
Its a 74 Dodge Charger, it sat for many years. I vacuumed the system for about 30 hour and it held for at least 5. I used 1 can of 134a stop leak and 2 1/2 cans of just 134a.
Air worked great...