just got me a '67 Barracuda

The odometer reads 84,200; there's no 100,000s on the dial.

It ONLY runs if I have the timing jacked way up, to about 20 or 25 degrees BTDC. If I try to turn the distributor so the timing mark approaches 0, it dies at what looks to be about 15 degrees BTDC.

Another guy suggested I do a thorough check for vacuum leaks, first. Reason being is that if I close the choke valve when the engine is warm, instead of dying, it revs up and smooths out. I've sprayed around the intake manifold, but not very thoroughly, 'cause I didn't want to ignite the stuff. But would a vacuum leak account for the bad timing?