Ford 550 keeps stalling

Having a continuous issue with my 550 stalling out after an hour or so. She'll run fine for a while then I can hear a change in the engine and it starts sounding like it's running out of fuel. Then when I try to restart it sounds as if it's loading up with fuel. Sometimes if I drain the fuel filter it will start back up, sometimes it just has to sit for a while. Any suggestions?

Ford 550 keeps stalling