I've got a '59 shortwide with the 4wd conversion. I'm running a 261 and the SM-420 four speed. I put the 3.38 gears in mine (front and back of course). I'm pretty happy with it but it's a pricey conversion(doubly so in my case). With the limited rpm range of the six I don't think you can expect more than about an additional ten mph from the conversion. Before I put the 4wd stuff in I had a three speed with overdrive and the conventional 3.90 axle ratio. The overdrive was much better than the 3.38. Unfortunatly it would have been too much engineering(for me anyway) to keep the overdrive with the transfer case. Another thought is the 5 speed T5 tranny. I think that would be ideal with the 3.90 ratio.
