Jim - If all you want is reduced rpms at highway speeds, just replace your stock 9:00-20s with 11:00-20s or 12:00-20s. A lot cheaper & easier than a trans swap. While you are at it, flip the hubs and run singles on the rear and improve handling and tire wear. If you can pony up the bucks, the Michelin 12:00-20 radials look really great as super singles! Don't forget to change the speedo adapter also, Saturn has the correct adapter for 11:00-20s for under $30, should be close enough for the 12:00-20s.
Don't expect to be able to run at "half the rpm's" at highway speeds in the Deuce. The engine doesn't have the power to hold highway speeds at 1300 rpm, unless you've built your truck up to a 300-400 hp monster. A 10%-15% reduction, say 2200-2300 rpm at cruise is probably as good as you can do without having to downshift for every tar joint in the road.
Also, don't expect too much noise reduction. Sure, the exhaust noise will decrease some, but the background mechanical noise increases greatly. I've been doing some sound level testing in my truck, at around 50-55 mph the background noise (engine clatter, gear whine, tire noise, metal parts vibrating and shaking, wind noise) starts to exceed the exhaust noise! If you want a quieter ride at 60-65 mph you will need to do some soundproofing as well. Remember, you are driving a truck designed on 1949 technology!
