Actually, '73-'87's were the R/V series, the '88-'98 pickups were the C/K body style. The Blazer/Jimmy, Subs, and crew cabs were the R/V series as long as they looked like the '73-'87 pickups.
Your source being....?
I was in the Oshawa Truck Plant from '85 to '88. During the changeover to the GMT400. We had never heard of the R/V designation until the carryover trucks were renamed.
GMC has used the C/K designation to denote 4 x 2 & 4 x 4 trucks since the 40s. See:
Also from Wikipedia:
Maybe it's a regional thing, and maybe every technician that I've worked alongside has been wrong, but every GM dealership that I have worked at referred to the body styles as such. In fact, I've got a 1987 GMC truck drivability and emissions service manual (for the R/V models) sitting next to me right now that has in parentheses "Includes 1988 C/K Models". I'll agree that if you go by the 5th digit in the VIN from '81 and up, every fullsize regulare cab or extended cab pickup is C or K, but that's just how I've always been told and referred to them. Maybe I'm wrong, but I sure as heck don't put alot of faith in Wikipedia.