Yes, you can definately use the newer driveshafts. Just drill the new hole pattern into the flanges 45° to the existing holes.
We were able to just use the ends of the new driveshaft as a template, used a sharpie to mark the holes then drilled.
Supposedly you can flip the crossmember around backwards and bolt up to two of the existing holes, and weld some angle iron on for the other two. i just had Bud at Budbuilt make me a crossmember.
He sells one now for the 1st gens that will bolt to your existing frame mounts.
My tranny tunnel was already hacked up from a PO, so I cant tell you if you will have to cut the shifter hole or not.
Basically this is all it takes.