This is just my biased opinion, but I think the GEAR VENDORS O.D. is the way to go. You get to keep your original tranny and low geared rear, and then you get the ability to overdrive each gear. It is the ultimate way to go for towing AND cruising, since you don't lose any low end grunt. I'm assuming you have an sm420 or sm465 tranny? Almost forgot, it's also expensive, but I'd do it again in a heartbeat.
