There is no difference. K5 is the badge/common name for Blazers and Jimmys, but all have the same suspension as a 1/2 ton pickup, so they're technically K10s.
K5 is the Blazer we all love, Wheel base is 106 1/6 inches The C-K10 is the pick up, The short wheel base is 117 1/2 inches long. The Blazer wheel base is 11 inches shorter. I was going to convert a 4x4 blazer into a 2 wheel drive by swaping the short wheel base pickup, but to wont work.