My favorite for mixed driving with a manual trans. has always been the 3.23 SureGrip 8.75. I've got a couple of extra pumpkins with different ratios sitting around (at one time I had it down to about a half hour to switch center sections- but I'm not that limber anymore :)), but I always seem to come back to the 3.23s. Good enough bottom end, and doesn't protest highway speeds.