I am doing a TPI to Carb conversion on my 87 IROC. I've removed the wiring harness that goes to the ECM from the engine bay. I din't find any cruise wires in that harness while doing that so I'm assuming that those wires are in the other harness that enters the car on the driver's side.

I don't know how cruise works so I'm looking for an explanation on that and maybe a little help making sure it will work with my carb setup.

 

Your mechanical speedo sends a speed signal to the ECM and another to the cruise module. Both via brown wires which come together at the back of the instrument cluster. Your cruise control should continue to function.

It's later cars that have the problem, since a speed signal is sent to the ECM where it's then sent to the speedometer and cruise control. So removing the ECM breaks that chain and you lose cruise functionality.