If I break anything while locked, it surely wouldn't be the 9" axles. Fear not about the mustang mounting points, if there wrong & can't be used I probably will ditch this idea, but I still think the idea us very sound. I knew the purists would bash the "smaller" rearend (1/5" smaller diameter ring gear), but I have an extra 8.8 out from under the Mustang in my avatar...I put an IRS from a '03 Cobra under it... What can I say, I'm a rearend swapper
My reasoning behind even considering the 8.8", other than that I already have the housing, is that I bought a Currie high pinion 9" for a J@@p CJ-5 with a Detroit Locker, 35 spline axles, Explorer rear disc (remember these are from an 8.8"

) and it cost a small fortune. I'm not under any misconception that an 8.8" can be as strong as that Currie piece (which I never ever had a problem out of, just the street driving quirkiness of a locker in an Uber SWB ride), but I think the 8.8" can handle a heck of alot of abuse if built properly & there is alot of parts & tech out there for them also.