Should bolt right up. The chassis' are nearly identical, and as far as I can tell the suspensions swap. But, you will need the corresponding axle u-bolt plates for whichever axles you're using as they do not interchange from dana 60's to 70's to 80's.
I'm getting ready to bolt in a set of Skyjacker softride springs into my '78 Ramcharger, 2. 5" over in front and 6" over in rear (I'm removing the 3" lift block completely so it'll be 3" overall in rear), and I'm using a dana 70 rear axle and dana 60 front. Now my Ramcharger is a big block gasser so it won't be as nose heavy as your CTD'd Ramcharger, but I bet the skyjacker springs will feel great even with CTD weight. May want to ask them if they recommend a different set of springs to support a Cummins. I bet they say no.
I should know about the 70 in a few weeks, and the 60 a few weeks after that. I'm getting an electronic diff locker for the ftont 60 - just coming out on the market - push a button, locks the diff - sweet and simple.
- Sam