Ford 8.8 Update
This is an update to an old thread I started, asking about using a Ford 8.8 rearend in a Gen 3 Nova. To summarize, the flange to flange measurement is almost exactly the same (60") but the pinion is offset 2 3/16 and the perches are off by about an inch or so. The rearend I got is from a '95-'01 Ford Exploder. If you get the tag that says 3L73 from this series you get posi, 3.73 gears and (I believe) 31 spline axels (at least mine has them and I have heard they all are). The 8.8 may not be quite as strong as a 9" but it is a LOT more common and is still a real beast. Supposedly the 8.8 is based on the GM 8.5 and may even have some interchangeable parts. Here is what I have done....
1. The tech dudes at Curry say the offset is not a problem; that it falls within the normal deflection for a u-joint.
2. Exploder rearends come with a weird 5" flange on the pinion, but not to worry, there is a saddle that bolts on it and NAPA has a u-joint with Ford on one side and GM on the other so it will bolt up to your shaft (NAPA PN PUJ-372 ... thanks Charlie!).
3. Brake lines on Exploders come in from the right side, but you can flip the lines on the rear axel and everything fits...well, it does with a 3/16 - 1/4 brake line adapter from NAPA ($6.09). Check out the pics./
4. If the eBrakes on the Exploder rear axel are even sort-of OK...keep them. Replacing the shoes is a major major B---- !! If you are brave (foolish) enough to try to replace them give me a PM and I will tell you what I learned

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5. I moved the perches. Some folks don't.
So the only other thing I have heard, which I have NOT tried, is that on an 8.8 posi (Ford calls it a limited slip, but what do they know?) you can replace the "S" spring with one from an F-150 and get more "bite" on the posi.
So...that what I found out so far................
Dave