Welcome to the forum Chuck
Basically the 350 will bolt right up to the motor mount brackets just where they are. Of course this is assuming that your I6 is a 230 or 250. If it is a 292, you will have to get a different passenger side motor mount bracket. You use the same motor mounts on the I6. You will have to remove the bellhousing crossmember, and install an auto trans crossmember. You can either use an original from a '63-'87 truck or go with an aftermarket one. Either way you will have to drill the mounting holes. If your current radiator sits down on the lower step of the crossmember, you will need the larger radiator that sits on the top of the crossmember. As for the column shift, there is a member that modified his 3 OTT column to use on a auto trans. I don't remember who it was, but he has a build thread in the 'Projects and Builds' section....I'll see if I can find it.