if you mean why did they use those particular numbers - cuz the engineer committee met w/ the marketing committee and the management committee, and the production committee, and they drank too much coffee, and close to quiting time said HAY! quick! gimme a number!
if you mean where's the meaning - the numbering scheme was a replacement for the previous letter designations, which were getting cumbersome and confusing - 3100 is the "generic" designation for 1/2T short truck, then the last numbers pinpoint the 'style' -> 04 = pu
beyond that the 3200 series = long frame, 3600= 3/4T, 3800=1T and such
Bill
