I have a 94 dakota and was wondering if you can swap out the 3.9l to the 318 without changing the running gear and if you can will the running gear hold up?

 

if your refering to the tranny and rear end if you dont abuse it they will hold up. If you take it to the track or just drive like your on one, you'll want to swap it out.

Also the heavier wieght of the v8 will give your v6 springs up front a slightly lowered look. and they will tend to feel like they are floating a bit more when you hit bumps.