I tore down a 1954 GMC pickup in 2004 for a frame up resto-mod. Within the first year I had the chassis done with a rebuilt engine, transmission, rear end, power front discs, new king pins, re-arched springs, etc. Then came the body work. It is still in my shop awaiting completion.
In the mean time I bought a running '56 Chevy pickup. I improved it a little at a time with it never being down more than a month at a time and usually not that long. I have installed a complete wiring harness, rebuilt the brakes, changed rear axle, installed a new Goodwrench engine, a new seat and more while enjoying driving it between jobs.
I now have the '54 Suburban and am approaching it the same way. Improve it while driving it.
I know there are many people who have torn them completely apart and put them back on the road but it didn't work for me. I breezed through the mechanical work but when I got to the body work, something I had no experience with, I got bored.
Tackling a complete tear down and rebuild is an enormous undertaking. I'd bet that for every 100 vehicles that get torn apart less than 25 get put back together. I'd recommend to anyone who does not have the experience in all phases of the build, buy one running and improve it as you drive.