I looked a while back for exact measurements of both these axles, but couldn't easily find them, so I figured I'd post them..

Ford 8.8 -
53" from backing plate to backing plate.
59.5" from flange to flange.

Chev 7.5 -
55.25" from backing plate to backing plate.
61.75" from flange to flange.

So, the 8.8 is 2.25" narrower than the 7.5.. That is 1.124" per side difference.. With some quick measurements, it looks like my stock z28 rims would still fit without much hassel, but they may look a little out of place being set in further..

Anyways, hopefully this info will be usefull to someone..

Cheers,