If you can get any kind of look at it, the original 273 bell housing is made of cast iron. A 340 bell housing would be aluminum. The 340 will bolt up to either bell housing. For the axle, look at the back of the center section. If it has a bolt on cover, it's probably the original, but could be an 8 1/4" rear, which would be OK. If it has a round back with no removable cover, you should be in great shape.