How the hell did someone wear out a 318, is what I want to know.
This isn't directly related to your question, but I think it's a good tip:
Go to the dodge dealer and get two cans of Mopar combustion chamber cleaner. For the first can, follow the directions on the can. (Run it through the intake at as low an idle as possible.)
For the second can take the spark plugs out, and spray the stuff into all the plug holes.
Reinstall the plugs and kick the motor over just a bit to mix the stuff up. Let sit for about 20 minutes.
Take the plugs back out and spin the motor over and let it spit all the cleaner and broken-loose carbon all over the engine compartment.
Reinstall the plugs, crank her up (it will be difficult.. you'll want a good battery) and rev her good for a few minutes. Then drive her hard for a few miles. If you've done it right, you should have some wonderful smelling black smoke, and you'll also have a much cleaner engine.
This worked wonders in my 97 Grand Cherokee. Also has the 318, with 76000 miles.
Edited to add, [b]change the oil afterwards.[/b]
Before you change it though, run a quart of tranny fluid through the motor with the old oil. Letting it idle for 5 minutes or so with it in there is good enough. Helps clean things out in there and helps freshen up your seals.