The motor brackets on the Dakota frame all bolt onto the crossmember. If the 4 cylinder brackets won't work (it would surprise me if they also fit the V6 or the V8 motors) the brackets simply unbolt.

We are talking about a rear wheel drive Dakota here, the Dakota 4x4 motor mount brackets are completely different, and the 4x4 Dakota also has a steering box instead of a rack & pinion system, and a different front
(and transmission) crossmember designs and locations. A Dakota 4x4 also has the rear axle below the leaf springs. A Dakota 4x4 also has torsion bars instead of coil springs like the rear wheel drive frame has. Rear drive and 4x4 Dakota frames are completely different frames.