just recently bought a 91 2wd, 3.9 auto, with 43k miles on it.....i've been reading on here bout using the autolite 3923 plugs for a little bit more power.....i went to autozone and they said it took a autolite 65 and a 3923 wouldnt work....they said that plug was for a 360 magnum..????

 

I just replaced the plugs in mine. Orielly auto parts computer suggested the autolite 3924 for the 3.9l. I just assumed the 3923 was a type-o in the post I read. The 3924 works great, but make sure you are using a good hot wire. I am running borg-warner wires, cap, and button. Also change that fuel filter if you have not done it in the last 10 thousand or so, it will make a difference.

 

they told me that a 3923 or 3924 was for the 94 and newer dakota's.....??? and that mine (91) def would have to have a 65 ???

 

3923 is one heat range colder than stock. Magnum engines work best at that range.

 

The guy told me 3924 for my 94 dak but I got the 3923's and it runs fine I would suggest them

 

I do not know to much about the 91s. The 92 model and newer use a different injection system.