68 3/4 ton 4x4 rear disc question ????

[jpmanyhearts]

I have a 1968 chevy truck that has drums all the way around I want to convert the front and rear to disc the front is pretty straight forward..............................I hope anyway the rear im wandering about if I could get some help I would really appreciate it. I could find a late 70's truck for the front but chevy didn't make a rear disc in the 70's did they ? then theres the matching of the gears or pulling my diffs out............wow this is beginning to sound like a LOT OF WORK, any way any info would help