Ok this may be nit-picky but on my seized 2001 4.7 and on the replacement 2001 4.7 I got the smooth, steel idler pulleys are both 3 1/2 inches in diameter. When I go to find a replacement at Autozone or Advance or really anywhere they all sell a 3 inch size. Does that make any real difference? Did the spec change to use a 3 inch one? Should I have even noticed?!!

 

not sure which the 4.7 uses. the 3.5" one i have on my desk looks to be an 11/16 bolt shoulder

 

I would just swap them and keep what was original to your Dakota the 4.7 was in many different size Dodge trucks and even Jeep's.