Suspension geometry analysis

[chevynut]

The 9 inch IRS Diffy case is wider, hence the narrowing of the half shafts to maintain the original width

I understand that, but don't understand why you're going through all that work to maintain a 63 1/4" axle width. Wouldn't it make more sense since you're building a frame from scratch, and you're cutting the halfshafts and making new toe rods, to go ahead and narrow the axle? I sure would.