You might clean up the headlight ground wire, they're in the engine bay, single lug wire landed on the front of the wheel fender. I can't think of why it would be affecting vehicle cruise speed but electricity behaves inexplicably at times.

 

I'll check that out. I have found if the speedometer is on 0 hitting a bump or a quick hit on top of the cluster gets it working so likely a cluster issue at this point.