I see you've really exhausted the search function.
BUT, since you are from Alabama also, I will give you a break. (insert dumb redneck southerner joke)
Anyhow, transmissions are interchangeable since the blocks have the same bolt patterns in the back.
You can use the crank and rods from a 4.2 to stroke a 4.0 into a 4.5 (4.6 or 4.7 if you bore the cylinders .030 or .060)
You CAN use the carburetor setup off a 4.2 on a 4.0 I understand, but thats kinda workin in reverse.
Bunches of stuff changes over; search or ask specifics next time.