Kary,I'm not sure about the vacuum drop before it dies,possibly just a result of the rpm drop.
Next time it happens jump out and open the gas filler cap.
You might hear a sucking sound.

If you do I'm thinking it could be a blocked gas tank breather,the fuel pump would soon be overpowered by the vacuum created in the tank and starve the carb.
It would be worth checking just to eliminate that scenario.

Last edited by jockbolter50; 08/06/2011 7:15 AM.
1950 Chevy Advance Design 3100 in Scotland
In the Stovebolt Gallery
More pix on Flickr.
I've definately got this truck thing in my blood ... my DNA sequence has torque settings
"Of all the small nations of this earth,perhaps only the ancient Greeks surpass the Scots in their contribution to mankind" Winston Churchill.