[GMC Jim]

MrShelley....my digi camera is lousy at taking pics close-up....sorry...I checked out the Rostra web site which seems very comprehensive..... I installed my control about 12 years ago and that model appears to be no longer available... The newer models appear to be even more versatile and offer several different sensing applications for cruise controls. On my control, the engagement switch replaced the turn signal actuating arm and was very much like the switch arm used in GM 'Cruise Master' applications.
I notice that Rostra's web site offers literature on their products.... and several types of cruise controls. You might wish to call them ( 1-800-782-3379 ) and ask about details for your proposed installation....Also ask about the various switches they have available ( replaces the turn signal arm) so that you can match the original GM if that is your desire....
By obtaining literature you can decide what you might want to purchase. Also, you can download the instruction manuals from their web site.
Your closest supplier for Rostra products is also listed on their web site. I notice that Rostra acquired The Dana Electronic Products division in 1991. I beleive Dana was the original manufacturer for cruise controls offered for our era of vehicles.
Keep us posted on info you are able to secure and the ease of installation; should you decide to install.