Go for the '63. I've got a '62, and absolutely freakin' love it, but the torsion bar front suspension is a wallet killer, as is a dual reservoir master cylinder conversion thanks to the hydraulic clutch. I also don't care for the '62 grill--it looks like an afterthought; they tool the twin headlight '60/'61 grill and just stuck a big cyclops headlight in the middle of it. The '63 grill is much better looking for the single headlight, but I like the '60 grill better with the twin headlights, and have added one to mine (I'm also going to add the twin-cowl hood with '61 park lamp inserts).
The '63 used a coil spring front suspension, which is easy to get parts for or convert to later discs by swapping in a whole junk yard cross member. Power steering is easier to add, and it has mechanical clutch linkage so there isn't anything to get in the way of the dual reservoir brake conversion.
They also started using the Truck 12-bolt in '63, which is easier to get parts for (though my '62 has the optional Dana 44, which is even easier and cheaper to get good parts for as it's still in production today).
As a little detail, the '60 and '61 instrument clusters could be had with full gauges, rather than idiot lights, and the '60-'61 kick panel vents were cable operated with knobs mounted under the dash. I like those better, and added them to mine as well. If you do, you'll need to add a notch to the kick panel for the cables to pass through.
If I had it to do over, knowing what I do now I'd look for a '63, but I wasn't really looking for a Suburban--it found me. The wrap-around windshield and knee-knocker cab is what does it for me.
-Brad
