Jeff,
In the twenty years that I drove my '49 half-ton with a straight axle, the biggest single thing I did to make it handle better was to add a front anti-roll bar set-up from a similar year panel. I also ran Camaro disk brakes and a '69 Impala rearend with 15x7 rims (S-10) and P235/70SR15 tires.
I put about 20,000 miles on the truck, driving all over the Northwest and never felt uncomfortable with it's handling. Once I got a 350 V-8 in it and the disk brakes on the front, I never had any problems with it going or whoa'ing either.
Prior to the anti-roll bar though, it was plenty 'twitchy' and would keep me on my toes out on the road.
