There are differences. I'm not sure where you found that they are identical. Most notably is the existence of the PCM coolant temp sensor in the lower intake manifold near the t-stat housing on the '96 that doesn't exist on the '98. The coolant temp sending unit for the gauges is located in the driver side cylinder head and has a different plug on it between the two years. 96-97 should be identical, but not 96-97 to 98+.

You have some choices. You could drill/tap the lower intake manifold for the additional sensor on the truck or you could swap the LIMs between the two motors. You'll also have to swap the sensor in the cylinder head.

If there are other areas where you are having trouble, you may want to fully detail them so we can help.

 

Same swap here.

Aunt wrecked her 98 last year 3 months after having a used motor put in it, found a 96 4dr 4x4 ( 98 is 4dr 4X4 also) with some engine noise (think something got dropped in a cylinder) and want to just swap the motors.

Is this an OBD1 to OBD2 switch over on the integration of the coolant temp sensors for the engine management computer sensor and the gauge sensor and are all the other sensors updated? I usually work on BMW's ( the german chevy lol ) and have an 88 GMC pu but you don't even need a book for that thing.

Swapping the LIM is easy enough over drilling and tapping which would require removal anyway. I figured worst case scenarion I caould use the heads and block and swap all the old sensors and run the old engine management or vice versa and swap the entire chassis harnesses and run the 98 E M system. Prefer option A. tho....

 

Anyone? I just got done pulling the donor motor today and the mechanic she had do the install left 3 of the bellhousing bolts off...

At first I was then I was

 

So you're good!!
Just get a set of Felpro LIM steel bound gaskets. Line up the Crank mark and dist rotor and dont move the crank after that {removing belt is good idea.} Then you can swap maniflods plus change out the head temp sensor. Put it all back togehter and you all set, with any luck

 

Cool any tips on how to assemble this the easiest way? I pulled the LIM and dist and all front acc off to pull it, seems like pulling the fender liner off hte 98 made it a little easier. Also are the trans electronics the same? The 96 has a leak around the control unit where the shift selector cable is and the 98's is dry. Trying to save as many parts off the 98 before we crush it to save some coin down the road like starter,tranny, alternator what else? 4wd case busted ear off but I suppose internals are fine is it worth keeping?