Truck Repair: Lack of horse power, vehicle speed sensor, fuel milage

Question
" I recently put a 1998 5.2L dodge engine into a 1981 Jeep pickup. The engine has 40,000 miles and the electrical has 150,000 miles. Engine runs and starts good, the fuel milage is about right but the horsepower isnt there. I got all the original wiring and sensors except the speed sensor from the axel and original fuel pump(including fuel system electrical). I used a aftermarket fuel pump and regulator so the pressure is correct. I have recently replaced the O2 sensors and fuel injectors. Is there any thing I could have missed, or have failed on the electrical side that would cause this lack of horsepower while everything else seems fine. I also had it hooked up to the computer at the local Dodge dealer but they couldn't help me any.

Thanks for your time
anything will be useful

Brian"


Answer
Hi Brian,
I haven't done any swaps like that, but I would suspect lack of vss signal, vehicle speed sensor, would put the ecm into limp in mode, and you wouldn't have full power. Might even keep the timing from advancing, but I don't know...just a thought.
Van