Farmall
It depends if it is gas or diesel. If I remember correctly, the gas was a 301 that ran decent. They had 2 diesel versions, one American, one German. The German diesel is the most desirable. They ran a little better but are a lot more money to work on. I doubt the rear end would be an issue, they used this rear end all the up thru 1066's although there are some differences, on the whole it was the same. The 706 rear end and tranny is used to build pullers because they will take the abuse with a few part updates. I would guess around 2k to 3k if the tins are straight and not rotted.