Can and how hard is it to swap out the cruise control off my old 91 Z28 5spd onto my 92 Auto?

 

You can but it might be tedious.

The multi function lever will have to be hooked up or replaced if doesn't have that cruise option on it. There are switches on the brake pedal too that need to be there.

I have access to info needed if you decide to do it. Catch me on here or Greenvillfbody as evolvedRS.

 

Is there a diffrence in the cruise control for a manual and a automatic? I have a pats car that was a 5spd.

 

I don't think so. You have an added switch though for the clutch release, which you won't have to add for the auto.