Also depends on where you plan to purchase it from. Salvage yard might be the cheapest place to go, the swaps can be decent, too, depending who's selling. E-Bay can get down right rediculous on the prices.
Just for a guidline, though, the average in my area (I'm including Indianapolis, as that's were most of the swaps i go to are) is around $100-$150 for a 3 speed overdrive, standard 3 speed is a little less. $ speeds can vary, depending on if the seller know what he has. The SM420 is a high demand off-road trans because of the deep first gear, lowest of any light truck trans. They can go from practically free to very high $$$. Can't really say about the HD 3 speed or Hydro-Matic, as I haven't come across any at the swaps or salvage yards.
