Not currently possible (without a lot of money) there was never a divorced 1356 case they are made out of magnesium and not aluminum. The case is not designed to support itself not to mention it is weak in the rear bearing retainer area and they tend to crack and leak there. Also the manual shift 1356 t-case is reasonably strong and reliable just keep it tight to the trans adapter and make sure the output bearing retainer is in good shape.
A ZF 5-speed from 97 to 07 models s542 or s547 come with the NV 271 or the electric shift 273 which is a little heavier but a lot stronger. Good luck.