Looks like a good buy. As a GMC, a few things will be different than Chevy, mainly a leaf spring rear with Spicer 44 with 3.54 ratio. Instrument panel, dash and wiring is a little different also. The worst thing about any old truck is a cheap repaint, big eye soar, especially in a different color. If the truck was left in original paint with patina, the truck right off the bat, would be worth 2 or 3 times as much. Luckily the interior still sports the original medium fawn paint from the factory. Here is a similar GMC ad in red in its prime. GMC did several ads in '65 in various colors, check em out on ebay.
http://www.ebay.com/itm/1965-64-GMC-...cAAOSwQiRUmgvC