I dont know about changine the tailshaft housings, I actually wanted the shifter location that it has now cause its alot closer and feels better. But yea, your going to have to measure for your driveshaft length. Take apart the driveshaft, and put in the front shaft and measure where it needs to be cut for the carrier bearing to sit in its stock location and then measure again from the ouput shaft to the axle flange for the driveshaft and calculate what needs to be cut for the rear shaft.

Actually, you might be able to get away with using the truck bellhousing on the 240 tranny so the shifter doesnt sit to far back if thats what you are looking for. But dont quote me on that, I'll check the spare trans I have in the garage tomorrow and let you know.