'98 coolant temp sending unit

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I've got a '96 4.0 cherokee and just recently replaced the engine with a low mile '98. Can't between several people find where to connect the coolant temp sending unit, it definetly isn't in the same place as on the old '96 engine. So the the temp gauge doesn't work! Does anyone know why this slightly important feature seems to be missing, or even better where the heck it is?! Thanks!