Tom,
Like Cletis, I have put a gob of miles on my strait axle truck in the recent past as well. I have 6000 miles on my 53 in about 8 months. Unlike Cletis, I see every reason to update the suspension. I have a '74 Nova sub frame that is going in my truck soon. It is the exact same clip as the '68 camaro's. The cool thing about this clip is that it is the same width (frame and backing plates) as your truck is now. You can also easily adjust the height on this sub frame so you can lower you truck.
Already set up for a small block, power steering, disc brakes, etc... Everyone uses this clip for a reason.
I understand the purists, but if you want to put in a drive train that isn't original, you might as well improve your performance and drive-ability while you're at it.
My brother's 56 F100 is set up like this and it is AWESOME!