You might think about a Buick 350.They came stock in 65 to 71 pickups and wagoneers. They make great power and parts are easy to come by. The beautiful part is you can find a p'up or wagon and drop the whole drivetrain including motor mounts and towers.Everything is stock so if you break something you can go to Napa and order a new one. They came with a number of trans. options including the GM turbo 400 and the T98/T18 four speeds.I had a 71 wagon with the Turbo 400 and 3.33 gears and it would pull anything I hooked to it and got good gas milage to boot.