1975 f250 460.

Drove the truck from home which is about 500 ft elevation, to Prineville,.Oregon which was about 3300 ft elevation. The entire driver there, the truck ran great. I was towing my boat and got to Prineville and the truck would barely idle. I started to drive it home and it was running great, got on a flat straight away and three truck started to make popping sound when accelerating and then it died at 60 mph. pulled over and tried to start it, Would crank, but not start. Kept trying and ended up having the carb backfire then catch fire.

What happened? Was the elevation high enough that it ran too rich and flooded? It has an edelbrock 600 cfm that I had bigger jets installed about a month ago. It is going back to the mechanic, but I would still like to have some idea of what might have been the cause.

Thanks.