Have you noticed any pinging? My dad has a 1994 Dakota with a 3.9 and 180,000 miles. It pinged really bad under part-throttle acceleration and pulling hills. The water pump went bad, so I decided to replace the timing chain at the same time due to the mileage. The chain was stretched, not excessively, but enough to just rub the tip of the drip tab. Just finished last weekend and it runs so much smoother and quieter. The pinging was nearly eliminated. The engine has quite a bit of blowby, so I plan to install some sort of PCV catch can to eliminate the pinging completely. BTW - I did pull the intake a few years ago and installed the Hughes Engines' Intake Plenum Repair Kit to seal up the bottom of the intake. If you do replace the timing chain, be sure to install a tensioner to eliminate the knock and clatter that is characteristic of the timing chain in the 3.9 engine.