Truck Repair: 1997 GMC Truck, gmc pickup, gmc truck

Question
I have a 1997 GMC pickup with 183,000. miles. I have had no problems with this truck and I have been the only driver and all maintenance has been done on time. I can be driving down the highway and the truck will cut off and all power goes off, including the radio. I can get it pulled over to the side of the road and turn the ignition off and wait less than a minute and crank it and it will start back up. The truck will not always cut off on driving it. I did take it to a mechanic and let him hook it up to see if anything showed up, but it didn't and he said that he would have to see it when it happened. I did have an alternator put in it, and this problem started right after, but I don't know if one has anything to do with the other.
I would appreciate any help in finding out what could be causing this.

Answer
Here is a test that you can do in order to find out if its the alternator.
1. Run the vehicle in park, turn on all accessorrys, lites, radio, heater, ect ect. If the vehicle dies, then you have a alt problem. I would quess, your losing power, and will cut out the engine... Ty..