Well, you said you can fab what you need, so what are you worried about?
Not sure about the 700r4 to 205. You might post that question in the 4x4 section. I went with a divorced 205.
The 6.2 blocks have the same 3 bolt engine mounts as any small block/big block. I used small block mounts on mine, but I had to modify my crossmember because it hit the pan. I'm not familiar with the big block mounts, maybe those will work better.