I just picked up an aftermarket cruise control at a rummage sale for $2-.
I checked the parts list to make sure it was all there (it was).  Upon
looking at the installation instructions I was getting the impression it
will be a pretty lenghtly installation project.  My father had installed an
aftermarket cruise on an '81 scirraco (sp?) so I feel confident it will
work out, just have to find a free weekend.  Good luck.
Chris