97 dakota 3.9 4x4 major issues. Need help.
 

I bought this truck about 8 mos ago and it ran wonderfully. Then about a month and a half ago, the issues started. It would randomly shut off on me while driving, and not want to start. I didn't hear the fuel pump kick on, and these trucks are notorious for fuel pump issues, so I replaced fuel pump, sending unit, etc. It didn't fix the problem and the truck actually got worse! Sounded like not all cylinders were firing. It would still randomly shut off on me, backfire, and didn't want to go over 20mph uphills. So i figured ignition issue. Replaced dist. cap, plugs, wires, rotor and took her out for a test drive. Ran and sounded great for about 15 min until i tried to go up a hill. I took the hill at 45, and truck slowed to 20 and sounded stuck in 4th... also sounded like not all cylinders were firing again. I have not had trans issues with this truck in the past and I just don't know where to look next. Any suggestions? I don't want to replace everything in the truck. I need this thing for work and I am losing money daily until I can figure this out. Any suggetions would be greatly appreciated.