The standard L, G, and W series transmissions and 21 spline gear driven transfer cases used with 22Rs and 22REs won't fit your engine, so you have two basic options.

1) Rebuild your current R150F transmission. Marlin does heavy duty rebuilds and can even add a lower first gear (big $$$) to it. You can stick with the transfer case you have now, or add a gear driven transfer case (I recommend the 23 spline) with an adapter from Marlin or Inchworm.

2) Source an R151F transmission and transfer case from a 22RTE turbo truck and use it with your stock bellhousing. This is what Bill Morgan has done, and it is a slightly stronger option and has a lower first gear, but these transmissions are hard to find. It CAN be a less expensive option if you can find one ready to stab in, but it can also be more expensive if you have to buy one and then spend the money to go through it. This transmission will bolt directly to a gear driven 23 spline transfer case without an adapter, they come behind the tranny this way from the factory.