The 3.90 was standard in '55-'62 so it's a relatively easy ratio to find. I got one for free and paid $75.00 for the other which is plenty cheap. The only other needed expense is a couple gaskets and new lube. Of course, if you're going to do it, it's a good idea to replace the bearings, but that's a small expense.
Next comes the drive shaft. You'll have to have one made or a used one shortened. I'm running a T5 with an adapter plate from Hamilton Intakes. I was able to use a stock/unmodified drive shaft from a mid '90s Astro van with the yoke from an S10 drive shaft which made it the perfect length.
Also, the .72 overdrive with the 3.90 rear end and 255/70/15 tires allows me to run 75 mph with my old 216 and the speedometer is spot on.
The entire swap (transmission, drive shaft, rear end) is so simple I was able to do it with simple hand tools (except for welding the spring perches) in the front yard in half a day.
