You said the Jeep tank is Poly.....why not just cut and mold a place into it for your existing fuel pump? Find a nice flat spot on the poly tank, cut an appropriate hole and drop your fuel pump in it (that is IF this poly tank is similar in depth as your existing tank). I'd use some good gasket maker that resists gas and other fluids to seal the pump in the tank along with a few self tappers.
I had a 80's something Ford Ranger years ago. The gas tank in it had rotted out a nice hole on the very top of the tank. I found it the first time I filled the truck up and went to leave the gas station and had Niagra Falls under my truck. When I pulled the fuel pump out of the tank, the clips that hold it in crumbled in my fingers. I patched the hole with fiberglass resin and matting and then put the pump back in its hole using the above mentioned method. Worked great! Drove the truck to the scrap yard after breaking the frame......yeah, we beat on 'er pretty good! It was cheap ($150) and fun....what can I say!?