My 1990 truck is a F150 4.9L runs rough will not start now.

First up u need to replace the starter

If it was running rich, it would run rough, and it likely fouled the spark plugs with carbon. Is so, cleaning or replacing the plugs will allow it to run again. But, the catalytic converter(s) will be damaged if they are not already.

The real problem is the rich condition. There could be many causes of rich mixture, dirty/sticking injectors, bad sensor(s), bad computer, clogged air cleaner, disconnected or problems with wires or vacuum hoses.