Electrical - over my head.

You'll need the wiring diagram for your truck, and the diagram for the latest model "carbed" truck you can find ('87 I believe?). Then grab a 12 pack and settle in for a couple of evenings comparing the two. You may be able to make your existing harness work, but if the instruments are driven by the computer, you may need an earlier dash cluster or leave the PCM in place to drive your dash. Not positive, but the computer may also have some control over the cabin climate control. Most of what comes through your bulkhead connector relates to body/chassis electrical; ie lights, AC, horn, washer pump, turn signals, instruments, etc. There are (IIRC) only 4 or 5 wires that operate the TBI, the rest are incidentals like cruise control, trans. lockup control, etc. depending on how your truck is equipped.
It may help to search some forums like FTO, Ramchargercentral, Allpar or some of the Dakota sites like dodgedakota.net for particular info- it's a fairly common switch in the truck world.