Van is running rough, back firing, distributor cap is clicking, no power n dies. on 1998 Dodge Ram 1500

I have changed the transmission fluids and gaskets, the oil pump, the ignition coil, used Sea Foam, changed the distributor cap and still clicks.....not sure what else it is. It also sounds like it may not be changing gears....sounds like a plane taking off. Have been told it could be transmission, camshaft sensor, distributor, fuel pump, bearings.....

Asked by for the 1998 Dodge Ram 1500