Even on later trucks that shared the same frame between 2wd and 4x4's,its never "easy" to make a 2wd into a 4x4...you need all the 4x4 parts off a donor (axles,t-case,tranny,etc),plus the spring hangers ,shackle bushing mounts for the front that must have a hole sawed into the rails to instal,and you'll be chiseling and punching rivets out by the bucketfull for a few days in order to bolt everything up......................................................................................................I believe a '65 truck would have had a divorced transfer case,a rockewell t-221 most likely-with a divorced t-case you can put any tranny you like in front of it,but they were noisy beasts,the straighter cut gears in those cases whine like a blower,and I'm not sure how beefy they are....you also wont have an easy job adding power steering or brakes to the early chassis...............................................................................................I have seen a few trucks that vintage put on later K-5 or truck 4x4 frames,thats an easier way to go,and you'll get disc brakes .P/S and a better suspension to boot...there is a nice '66 Chevy stepside on the Boston CL in Glouster MA for sale thats been placed on a K-5 chassis and it looks sweet--if I had 6 grand ,I'd own it!....those years (60-66) are among my favorite trucks as far as looks,the 55-59 second series are real cool trucks too...I'd love to find a 60-66 Panel Suburban 4x4 with barn doors!...the '61's with the big eyebrows on the hood look really mean!...