You'll have to move the spring perches on the 70, 1 ton rear springs are more narrow than 1/2 and 3/4 tons. The shock mounts are positioned differently as well. The front 60 is 95% bolt in with the possible exception of brake hoses (depending on year). The rear u-joint on the 70 is different but you may be about to cheat with a conversion u-joint.
Now the hard part.... The dually axles are considerably wider than single wheel axles so stance and wheel selection come in to play. Regular wheels will give the truck a super wide stance and you'll have to watch the front tire for fender contact as it will have a larger front to rear sweep when turning. A popular option when using dually axles is to go with H1 Hummer wheels. The H1 wheels have a negative offset that tucks them under the truck more, when used on the dually axles they will give a more normal stance.
You can search the "Garage" forum for threads about this conversion. Honestly, you're not going to find a lot of example trucks that use a rear 70 but don't let that discourage you, it's a fine axle to use.
