I wouldn't reccomend using an old used fuse box. Try our host or http://www.americanautowire.com/ . The wiring harness on these trucks are very simple. Use 1963 Truck manual plus the 1964 supplement to guide you through this process.
For factory-correct connectors, colors, gauges, quality, fit & finish, give this outfit a try: www.wiringharness.com M&H Electric Fabricators, Inc. 562-926-9552 Classic Parts also has nice reproduction harnesses for the '60-'66 Chevy trucks.
I just got back from the Chevy truck junkyard in Santa Ana. 2 used harnesses with a fair amount of corosion on the fuse holder , will take some time to clean and get a good connection. 100 bucks, I don't have the dough to get a new one at this point. Hope I'm not putting a band aid on a hemorage.
I just got off the americanwire website a new fuse box is 110.00 why not buy that instead of 2 used ones....???
Painless is neither painless, unless you are accomplished at automotive electrical wiring practices & techniques...nor painless to your pocket book.
I used a wiring harness from EZwiring 21 circuit ,bought it of ebay including shipping it was 170 dollar. It is easy to install and had no problems with it.
I made my harness from scratch. Bought a bunch of diffrent colors and tried not to use the same colors on the same harnes. The 60's truck is broken into 3 basic harnesses. Using a wiring digram I was able to trace it all out. You can buy the locking connectors and reuse the factory connectors. Once each harnes was completed I would use Scotch #88 to tape it all together. Scotch #33 will also do the job. I didn't spend anywere near $500 to get this job knocked out. Also I up sized the wire on alot of the circuits. The lights are a little brighter and it starts better. I used welding cable instead of off the shelf battery cable. It's larger and more flexable.
Classic parts has a great one. I used the wire harness from Classic parts and the fuse box was just like the original one. Took all of 30 minutes to install, super easy.