My 79 K10 had this. Dead serious. 34 tooth ring and 10 tooth pinion. Rear axle only though. Front axle was 3.42.
I've read in a Chilton's manual that most 4x4 axles from the factory are not "exact matches"...as an example,they show a 4x4 with 4:10 axle ratios,in reality,the front axle has 4:09 ratio,due to differences in ring gear sizes its not possible to get them matched perfectly..but "close enough" so no ill effects will be noticed...