If it is the 3.90 gears grab it, they aren't real easy to find, and are popular for this swap.
If storing it is a problem remove the center section and keep that part and dispose of the rest.
$40 is real cheap for 3.90 gears. If its the 4.57 I'm not sure it would be worth the hassle. What gears do you have now?
You're going to end up with one full rear to dispose of whether you swap the pumkin or complete year, so if your brakes, bearings and seals are good I would swap pumkin only.
