Frank, the 89 has a lockup converter. The 87 has a Starion cruise system partially installed, but I never got the vacuum pump to work, and since there's no manifold vac at cruise in the TRaider (I get about 1-2 psi of boost at 80 level cruise), the vac actuator on that system won't work, and you have to find room for a vac reservoir, vac pump, about 4 valves, a couple of vac switches, ....

I may give up and install an aftermarket system, but the Starion Cruise control stalk bolted in so nice to the column, with only very minor notching of the column cover.

The fsm shows diagnostic codes for the cause of cruise cancel which is stored until power off. Read the leftmost diagnostic terminal pair, connector up. page 14-119 of the 89fsm in the engine controls pdf.