Although anything is possible with enough money, I don't think that would be a bolt-on modification.
The front drums are wider than the rear ones, so the distance between the axle and the backing plate is off from the start; assuming they fit with the rear backing plate. My guess is that if someone wanted to do this mod, he would need to fabricate a new backing plate from scratch, with an offset on the axle and adapted for a mix of rear wheel cylinders and front wheel shoes.
I guess if it was easy, it would have been done by many a long time ago.