I did the crossmember swap on my 1960 GMC back in 1997 specifically to get rid of the ball bearing front wheel bearings. When these trucks were new ball bearings were the industry standard and cost about $5 per side for both inners and outers. Now they are closer to $100 per side and made of inferior materials and don’t last as long.
What I didn’t know at the time is that the hubs can be changed to 1962-63 hubs (I’m not sure which) that came with tapered roller bearings to begin with. For a locally driven truck, there’s nothing wrong with the original suspension. As K10 points out, the parts are more expensive but the ride quality is superior, and adjustable. And once everything is replaced it will probably last another 40 years before needing attention.
My truck is a hot rod and I wanted 5 lug wheels, so the disc brake swap was the way to go. It was also a long distance freeway daily commuter, and I wanted the benefit of the disc brakes. The only real advantage beyond the improved braking is if you want to lower your truck. There are far more options available in the aftermarket for the coil spring suspension. Many owners with t-bar suspensions simply back off the adjuster bolts to lower the front end, but if done to excess the adjuster arms themselves hang down far enough to be a road hazard.
Should you choose to do the swap, here are a couple of links that show how I did mine. The first link is the suspension swap and the second pertains to engine and transmission mounts. You can click on the photos to see them in a larger format:
http://67-72chevytrucks.com/vboard/showthread.php?t=366850&highlight=front+suspensionhttp://67-72chevytrucks.com/vboard/showthread.php?t=369663&highlight=front+suspension
