My 99 Ranger 4 door extended cab has the cab corners rusted out. I have looked high and low for a repair panel but I see nothing for the four doors except the entire piece that runs from the top of the cab down to the rocker. Has anyone else been able to find a solution? Thanks in advance.

 

LMC truck show 3 different cab corners, here: Truck Parts and Truck Accessories

You should be able to adapt one for your use

 

If its not too bad try to body fill and repaint, if not, junkyard cab