If you just had the left arm PM you could get away with just moving the left arm as long as they were the same length but since you have a dual arm PM you have to move the whole crankset anyway. If the bike already has a Shimano crankset it will have a compatible BB and if it doesn't BBs are cheap and a shimano compatible BB will fit in every single frame you are going to come across. There is nothing special about shimano cranks or their BBs pressfit threaded whatever. You probably need to go talk to a bike shop.