Easier and stronger to swap the 2.8 box out for the 4.2 4.5 zd30 box etc, keep 2.8 transfer so you don't ned to change tail shafts and diff flanges, the transfer will bolt up with a small mod.
I don't think you can get an adaptor to join the 6.5 to 2.8 box.
I don't think you can get an adaptor to join the 6.5 to 2.8 box.