I've been looking for a rear end for my fully fendered Model A coupe build. I have found a few 9" Ford rear ends but none the size I need. ~58". So here are my questions.

1. Can any 9" ford rear end be cut down?
2. Does it matter if it's a 28 or 31 spline?
3. If I want to change the ratio, is it really as easy as changing out the chunk? (Is that the right term?)
4.Since I need to have it cut down. What would be the perfect width for a Model A coupe, wms to wms? 56"? 57"? 58"?