The thing I see, is with my 67, half of the bed is rotted away, and the rest is so deteriorated that I wouldn't trust it with much more than 600 lbs (had about 650 on it this summer, I was terrified it'd break through). On the other hand, there's a 68 GMC 1/2 ton that's been in the same region all it's life with a steel bed. Aside from a few dents, there are 5 quarter-sized holes in the bed, and the rest is in really good shape. If I was going to buy a truck back then and it was going to be a farm truck, I'd pay the extra cash for a steel bed, simply by what I've seen with them now. It just seems to me that the steel beds last longer, look better longer, and would be cheaper and faster to manufacture, once the technology was up to it, like Fred mentioned.