Kinda forgot about this thread, but thought I'd give an update on the spark plug non-fowlers. No codes for the cats in almost 2-2.5 months now, so I'd say it's a success. Don't know if it's any different for other trucks, but for how cheap they are, they are definitely worth a try.
For my 97, all I had to do to make the O2 sensor to fit into the non-fowler was to drill a 1/2" hole on only two of the four non-fowlers.
I didn't have to do this on my 98, since I was able to have one of my college instructors delete the cats through HPTuners.
I will have to remember to update this come winter to see if they still work. My 98 used to give me codes every once and while when I had the cats still on it, but only in the winter, never in the summer, so I will be surprised if these non-fowlers keep the codes off in the winter.