HO 52 and HO 72 internal parts do not interchange. The complete carrier assembly will swap. The 4.10:1 ratio is terribly scarce- - - -us round tracker guys used most of them up in the late 70's/early 80's in dirt track cars. There will be a lot more replacement parts and a better selection of ratios with the Dana 60's, but a lot of the axle housings are too wide to fit between the fenders very well in a a 3/4 ton. A 1-ton flatbed chassis with dual rear wheels (Dana type 70) won't have as much of a tire clearance problem- - -no fenders to deal with! Duals don't work well with a type 60, the hub bearings aren't heavy enough for the load range of dual wheels.

Don't worry much about a whine on a float condition- - - -they will run for years that way!
Jerry


"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!