I *think* that you can use a cruise control set-up out of a gasser, as well. If so, that would certainly make it much easier to find - like at junkyards. It may have been talked about here on the forum before - try a search. Or, just call a dealer. But, yes, that is all that it would take. The programming is already in the ECM.
1998 K2500 Suburban 6.5L TD 3.73 rear, Ron Schoolcraft 18:1, Kennedy ECM & IC, Timing gears, Splayed main caps, 3.5" Kennedy Exhuast/No Cat, K&N Filter, Boost/Tranny Temp/EGT(Pre Turbo), Ceramic-coated Manifolds, 195 Stat's, 265/75's (VSSB Adjusted) 7,000lbs (on a scale) Remote Mount Oil Filter, Remote Oil Pressure Sensor