[Mikado14]

hmmmm,,,, the original problem was that the ignition was not advancing. How did the mechanic know it was the distributor?

My first guess, and I don't like guesses would have been to check the knock sensor.

Did he scan the engine with a scanner and review the data?

I will tell you one thing. Had a Blazer with a 4.3 vortec in our shop a while back but I can't seem to remember the year. Anyway, this too needed a distributor. We put one in, ran fine for a while, then another, ran fine for a while, and then another. When the third one went out on warranty we started to look into it. Here it turns out that the distributor was not being grounded properly. A little emory paper and it hasn't been back since. At least not for the distributor.

I would definately recommend a scanner to look at what the engine is doing and put the shotgun back on the rack.

JMHO, Good Luck!