I HAVE 2003 SUPERCAB Ford f150, 4.6L, automatic, 3:55 ratio rearend 1/2 ton, I need to know how much trailer it should be capable of pulling, (size.weight etc)?

Look up the GCVWR (Gross Combined Vehicle Weight Rating)in your trucks manual.
Then subtract the GVWR (Gross Vehicle Weight Rating)listed on the sticker in the truck's door frame. That's your max towing capacity with a loaded truck.