i have just bought a 1985 dodge 100 with a 318 everything is stock i found it sittin in a barn for 8 years and i like to go play in the mud alot but i have to drive it on the highway to so i would like some tips on what to do to it so i can drive it in the mud an have fun where i wont tear it to pieces like my last truck but yet drive it on the road an not hurt it either  

first save up around 1500$  then spend 1000$ on whatever you wanna do for your d100, then take the other 500 and buy a geo metro for the highway( plus better gas mileage) or if you wanted to spend all 1500$ you could go down the side of the road if tires are what your worried about no asphalt no problem....!

With the 318, you can't go too crazy with bigger tires without changing the axle gear ratios (about $500 if you do it , about $1000 if you pay a shop) I don't know what your stock gears are, but the are probably pretty high like 3.07 or maybe 3.73. If you have 4.10's you should be OK for now. So I would start out with a rear "lunch box" locker, probably a Power Trax Lock Right or No-Slip, or Detroit EZ locker that replaces your stock spider gears in the differential (about 1/2 the cost of a full Detroit Locker and you an put it in yourself) and the biggest tires (no bigger than 35" with stock axles and gears) you can fit at stock height or with a mild lift about 4". You can always cut the fenders out if you need more room later. I like to ProComp Xterrains, (good for both street and mud), remember the better the tire is off road, the worse it will be on road, so take that into consideration when looking at tires, sure swampers and boggers look cool and go like hell off road, but are not so asphalt friendly and will wear out fast.   A rear locker and some aggressive tires (even stock sized) will improve the off road capabilities tremedously, if you can add a small lift that will help you fit bigger tires and improve ground clearance. Wheel the heck out of it until you break something and have to upgrade, or you have saved some more cash and are ready to go bigger.  It's a vicious cycle, bigger lift, bigger tires, then bigger axles and lower gears, new driveshafts, bigger brakes, bigger motor....