I agree with the piece at a time approach. I tore my '54 GMC to the bare frame 6 years ago and it is still in pieces. I bought my '56 Chevy 4 years ago and have replaced the harness, brakes, rearend, engine, seat, headliner and more a piece at a time. Never was it down for more than 2 weeks. I've put over 12,000 miles on it while doing it.
I just bought a '54 GMC burb and I'm going the piece at a time route on it. I just got the new power discs in it and waiting on new wheels to put it on the road, faded paint, shabby upholstery and all.