I would change the gears, then see how it works out and go from there.

 

for me i would keep dodge with dodge chevy with chevy ford with ford but thats just me

 

AMC use to mix match GM ford dodge etc... just make sure what transmission, tork converter and transfer case can fit your engine after you may need custom made driveshaft.

it sound like a good idea but it will be a painful swap but some guy perform a 5,3-6,0L swap in offroad vehicule with a simplified harness for swap for really cheap dont remember the company

 

If your going for more mpg's and power, buy the new RAM. The 4.7 HO isn't the motor u want to use for me mpg's or power really either. Switch the gears out first to see if that helps at all. But the average mpg's for the 4.7 are anywhere from 12-18 average bring the key word. If ur hauling ur looking at the low end if not worse. What kinda mpg's r u gettin w/ the 3.7?

 

why not just sell the truck and get one that meets your needs cause your gunna spend crazy money trying to get everything swapped over and trying to work