I have had a 94 3.9 (4 yrs) and my present 3.9 for ten years she is a 1999 and neither has ever let me down in any way, neither have ever seen a battery minder either but I always throw the red isolator key when not in use.
I believe the later 4.0 Ltr power units were heavier, likewise the 4.6 Ltr and that's why I chose my models.
Good luck in your choosing.
