[LILRED66]

Per the literature I have, here are the following production numbers for the '65 and '66 model years:

1965 K10 1/2 ton swb chassis cab 48
1965 K10 1/2 ton swb stepside 1,127
1965 K10 1/2 ton swb fleetside 633
1965 K10 1/2 ton swb Panel 103
1965 K10 1/2 ton swb Carryall (barn doors) 444
1965 K10 1/2 ton swb Carryall (gate) 433

1965 K10 1/2 ton lwb chassis cab 52
1965 K10 1/2 ton lwb stepside 513
1965 K10 1/2 ton lwb fleetside 1,459

1965 K20 3/4 ton lwb chassis cab 308
1965 K20 3/4 ton lwb stepside 889
1965 K20 3/4 ton lwb stake 1,364

1966 K10 1/2 ton swb chassis cab 40
1966 K10 1/2 ton swb stepside 1,123
1966 K10 1/2 ton swb fleetside 678
1966 K10 1/2 ton swb Panel 170
1966 K10 1/2 ton swb Carryall (barn doors) 530
1966 K10 1/2 ton swb Carryall (gate) 418

1966 K10 1/2 ton lwb chassis cab 30
1966 K10 1/2 ton lwb stepside 457
1966 K10 1/2 ton lwb fleetside 1,976

1966 K20 3/4 ton lwb chassis cab 431
1966 K20 3/4 ton lwb stepside 924
1966 K20 3/4 ton lwb stake 1,796

I don't remember the website I pulled this from, however I printed it out and saved it for threads like these.

Here are a couple pictures of the factory 4x4 trucks I have.