I've got the original '92 Dakota fuel tank and pump, as well as the return style fuel rail. The truck is up and running (not driving yet though) with the newer 5.9 pcm, Slowly moving through the next steps.
If you hooked up the vacuum port on the FPR, I think you will find that you will have drivability issues down the road. The PCM expects a steady pressure but the vacuum port will cause it to fluctuate with will in turn cause the PCM to mod the tables (as much as it can). And I think it becomes a merry go round of changes that the PCM can't fix and makes worse. It probably idles and drives fine, but I think the more you drive it the worse it will get.
Guy I follow used a truck PCM in his Barracuda when he swapped the '94 GC 5.2 into it because he needed a stick PCM. The '94 GC still used a return style fuel system but I think the truck PCM he used didn't. In the end he tossed the PCM because he figured it was faulty. It very well might have been, but I suspect it was (at least in part) because the PCM couldn't adapt to the varying fuel pressure. In the end, he said it ran significantly better with the earlier PCM.
Not telling you the story to try and support my idea, only to say that if his issue were related to the fuel system mismatch, it wasn't just a surge once in a while, it kept him chasing gremlins until he tossed the PCM.
