You will have to move the perches on the rear axle. The 67-72 1/2 and 3/4 ton perch spacing is the same as 73+ 1 ton perch spacing, if I remember correctly and have my bearings straight.
the front axle will be no problem, all solid gm front axles have the same perch widths. however, you don't want the front axle (dana 44-5F) from a '69 because it has drum brakes and closed knuckles. My '69 was fine for a DD with that axle, but with bigger tires it'd be scary. not to mention if you got the brakes wet at all, it was scary.
also, the rear axle could be either a dana 60 or an Eaton H052. both are full floating, the D60 had an option for the powerlock posi from the factory, and the eaton had the option of a detroit from the factory. the eaton looks like a ford 9 inch on steroids.
