Well, today I pulled into Plant Equipment Company (PECO), yanked my A/C hose (he he) and walked it in. They replaced the damaged hose with Aeroquip while I waited, and charged me only $13 bucks + tax. Then I went home and replaced the expansion valve with the one for the non-intercooled truck (it's the only one I could get), made a pigtail to clear the A/C motor housing and put it all back together. Then I pulled a vacuum for 20 minutes. Then I started to add R134a. After only 1/2 a can, the A/C line going into the H-valve got cold. I finished the can and the outlet temp in the truck felt pretty cold. The sight glass was still bubbly, but I decided to stop there and test (note the recommended is three cans). I went for a drive with my temp monitor in one of the ducts, and the temp went down to 31.9 degrees at one point! It never went above 38 deg the whole trip. This is colder than my A/C has ever been the whole time I have owned the truck. I have even had the "pro's" work on it, sucking it down for an hour and all, still it's never gotten down into the 30's.
Conclusion: I think R134a works best with WAAAY less head pressure than R12. Either that or my truck is possessed, which I have a strong suspicion of...