Since your 1957
Bubble pre-dates the adoption of Dura-Torque Axles that began in 1961
, your coach should have a straight axle with leaf springs. If you read any of the accounts regarding the Cape Town to Cairo Caravan or the Around the World Caravan, you will read of just this technique being used to gain ground clearance on the pre-Dura-Torque axle equipped coaches.
I can't fill you in on any praticular details as all of the coaches that I have owned had the Dura-Torque axles. It would appear, however, that the two tasks would be relocating the spring monts and possibly the shock absorber mounts.