yea  i don't think theres much that can be done with the auto tranny trucks

Trust me I know.  The auto tranny is one reason why my 3.0 is lying next to my truck.  Its definitely not going back in.  I'm currently looking for a 3.4 to take its place.  At some point in time I plan on running as large as 42's, what kind of dual case gearing do you guys think would be best for this?  I plan on using the MC10 so I can use my 88 tranny and T/C. Would the 4.7 reduction unit be a good idea to mate to my 2.57 chain drive T/C?  I ask this because I don't want to be running a chain drive case if it cant be handling these gears also if this would be a good set up for 42's.