i kno that tha reason that tha 04 v-6 is a 3.9 cuz of tha intake so if i use 3.8l performance parts am i lossing performance n if i use tha 3.9l parts is it gona be tha same... i would juss bye tha 3.9l parts but there hard to find

ps. if anyone knos a place where i can find 3.9l parts let me kno

 

The Feb issue of MMFF Horses Mouth section explains this "the mustang shared ther 3.8 engine with the Windstar and when Ford launched the minivans repalcement, the Freestar, it changed the engine slightly and it became a 3.9 . Even thought the Mustang only had a short model yearleft, they were forced to follow suit with the change. As it turns out , most of the 04 v6 Mustangs built feature the 3.9, which is the same engine,justa with a slight overbore. Horsepower is said to be the same with the miniscule increase in displacement."

Production #s
04 Mustang 3.8L =17,842
04 Mustang 3.9L =74,972

 

so if i use tha 3.8l parts it wont hurt my car... tha only reason is beacuse when i see tha parts online and how there listed is like for v-63.8l 99-03.. and idk if it will fit or if its not gona get tha rite output

 

I read from a ford ad online that the 3.9 was actually stroked not bored.
The bore for the 3.8, 3.9 and 4.2 are 3.81in. Where as the strokes are 3.39, 3.48, and 3.74in. The only differences that I know of are the stroke and a different computer. So any mods that you do that don't affect the crank or the computer will work for 99-04 V-6s. Except headers fit 01-04 or 99-00.