okay check this out to help you even get more confused.
91-92 did not have a cam sensor, they just have a little block off plate where the distributor would normally sit on the 2.9L (oil pump drive cover)
in 93 they typically did not have this sensor either, UNLESS the truck was a CA vehicle, then the 93 had EGR and a CAM sensor.
in 94 they all were like the 93 CA version, with EGR and a cam sensor.
So your 91 computer does not even have wires for a cam sensor, so it wouldnt matter if it was in your block or not.
if you are using a 2000 lower intake then you are using the 2000 upper as well?
I know the depth of the drive gear on the cam sensor varies depending on which lower you use, but I didnt think the 91-94 lower intake would work with the 95+ plastic upper.
And then of course in what 98 they went to the returnless style fuel rail?
You see it can all get very confusing
But bascally there are 3 4.0L engine blocks, the 91, the 93 and the 95+ with the 95+ being the strongest heads and casting.....lets not even get into compression numbers and swapping heads

or running SOHC pistons, etc...