you only have on collector gasket on your passenger side, the other is a ball joint. it should be sized for a 2.25 inch exhaust system, but it is an oval shape and could be confusing to measure. just go to your ford parts dealer and ask for one.
AFAIK, there's no gasket on the driver's side...it's a ball and socket joint.
On the passenger side you'll need a Ford gasket (or an equivalent) that looks like this: