Hi, I have lived in a 1991 Dodge just like it, but blue, for over 6 years. The only thing I can say is mine has been very reliable. Even when I haven't stayed on top of maintenance the way I should. Mine is a 3.9 V6, but the 318 is a great motor and it would give you more power though less room to work in the engine compartment. Some things to watch for. Plastic bushings. The ones for the transmission linkage went out the first year, but in the last 6 years have given me no trouble. The plastic bushings for the windshield wipers went out twice in 7 years. I just keep a set in the van now. Power windows. You cannot get a rebuild kit for the motors anymore, so you have to replace the whole motor and junkyards want to sell you the whole assembly with the regulator even though the regulator will most likely never go bad. The main thing is oil changes and tune ups. Keep up with them. I had to replace my water pump 2 years ago. A real PITA with no air tools, but it took me about 3 1/2 hours by hand. You do not have to remove the radiator to do the pump, but you do have to take off the alternator, PS pump, AC compressor, and smog pump to get it done. Most bolts on the van are metric. Keep that in mind. It is most likely OBD1, so you do not need a scanner to get codes from the computer if you have a problem. That reminds me. The main power relay for the computer. Learn where it is before you need it and keep one in the glove box or something. If it goes you are totally dead in the water. The engine will crank, but you will get no fuel, no spark, and no codes. If you have any questions, feel free to ask.
Honestly, I am a Ford man at heart BUT this van has paid for itself and been very reliable.