I have been shopping around for a "better rear end" set-up too, and considered the 9", and the 8.8. I finally took the advice of my father and uncle, whom have raced fords most of their lives....stick with the stock 8" and just throw in some gears....cost a lot less and less headache. If ya got so much HP that it can't handle it.....then worry about it then.
Oh yea....you can modify your 8" to have traction-loc capabilities. Just hafta order a couple of washers from ford. But for the daily driver like me....don't need it.
gulupo, i,m getting ready to do the 8.8 swap, did you find out how the late must. rear compares in width to 8 inch in the mav's. does anybody know the width