1949 chevy 3100 rear end questions

[ryans69chevy]

hey, my dad and i are working on a 1949 chevy 3100 1/2 ton (or so we think). It was used as a grain truck on my great grandpas farm and nobody really seems to know much more than that about it. the front end has a 6 bold pattern where the back end has an 8 bolt. the rear end is jacked up so high also prob so the extra weight wouldn't effect it.

were wondering what rear end from what other vehicles we could get to fit under this pickup without any modifications? we want something that can do good on the highway since we aren't planning on towing anything with it.

Thanks!