Who knows what about early 8-3/4s?

i'm gonna guess that originally came out of a bigger truck or a tractor. the splined axle shafts are typical of smaller tractors like gravely, small massy and fords. the trucks-- larger ones, used the same style and with what looks to be way bigger than 3" tubes on the housing that would track.

my guess would be late 50's flat bed.

the pig is probably the only thing you'll be able to use. unless you got brakes with it. but mannn, those are gonna be heavy.