No problem: Use the existing setup. your vehicle uses a separate control module and imputs its speed from the reed switch in the rear of the speedometer. So even if you use the GM sensor for engine management, it will not affect the cruise control. Your only problem will be mounting and adjusting the actuator so that it will work on the GM linkage.
Good luck
Conner

Over the hill but still climbing.
88 Montero 2.6L auto, manual hubs, cooling fan conversion gps,recurved distributor,LSD Diff.