I don't know if this is relevant info or not, but I discovered a couple years ago the Dodge used 3 different transmission mounts between 1992 and 1994 Dakotas. The 93 was a changeover year, and neither the 92 nor the 94 will work without modification, and the 93 mounts are no longer available. The truck I ran into this on was a 4x4, but I've heard they did the same thing on the 2x Dakotas.
I had to modify the crossmember to get the 94+ trans mount to work. Maybe you have the wrong crossmember for the mount you are trying to use?

I sure hope you guy get this figured out, I will be putting a 96 318 4x4 drive train on a 91 4x4 chassis soon, and will be covering this with 49 Dodge sheetmetal. I'll have enough to deal with making the sheet metal work, I don't want to have to deal with a motor/trans issue as well, but I will if I need to. Gene.