I think it would be 6 of one, half dozen of the other whether to transfer all the 4wd components to the '65 frame or mount the '65 body onto the '79 frame. The biggest thing to consider in that decision is what is required in the state of Texas when switching frames, to make it 'legal'? You don't want to do the frame switch, and then have title/licensing issues.
A short while ago, I started a thread with some pics of mounting a '60-'66 body onto a '73-'87 frame and running gear. That one is a 2wd, but the body mounting would be the same, but you will still end up with aprox a 3" body lift. Here is the thread.
http://www.67-72chevytrucks.com/vboa...d.php?t=481023
Personally, I would transfer all the running gear to the '65 frame. I haven't done one like that, but I would just use the '79 frame as a guide. The frames are still very similar.