Although I am a proponent of Steele Rubber Products for all of the rubber products you can order for the 60-66 GMC (and Chevy) trucks, I am not too fond of the door weatherstripping- it is very tough stuff and your doors WILL NOT close because there is so much resistance to the gap between the door shell and body channel. I took to another outfit, SoffSeal.com and found that their door weatherstripping is much softer, but does provide for a good seal, and your doors will have no problem with this product.
http://www.soffseal.com/store/main.a...tail&item=9008 $77.62 + S/H