I do know about the aftermarket floaters and parts for the 9", and I'm certain you can get whatever bolt pattern you want for one, but I'm thinking more about easy and cheap parts the average guy can get at the local salvage yard without spending a bunch of hard earned cash.
Not trying to start an argument or anything, just pointng out the easiest and least expensive way to do things and still retain some capacity.
As far as interchange, Chevy used the same axle for 3/4 and 1 ton up to '72, with a 4.10 gear available from '68-'72 in 3/4 tons with automatic.
