1990 B150 Dodge Ram Vans runs great until it's warm then stalls and stalls...

Sounds like the automatic choke is not closing soon enough, so as the engine warms, the mixture stays too rich. That could explain the back-firing as well. Un-burned fuel is getting into the hot exhaust or catalytic converter and is being ignited there: Boom! You probably need a new choke stove, which contains a bi-metal strip which curls up as it is heated (or un-curls, I can't remember which) and is supposed to pull the choke off as the engine warms up, letting more air into the carburetor, leaning out the mixture. It is not an expensive part, and doesn't take long to change.

My Computer failed that adjusts the mixure.Dealer has rebuilt ones still available

Problem solved, it was a distibuter coil relay. Thanks for all of your help... cheers.