Well after finally getting trans in and sorted out I thought behind new then rebuilt 486-498, had spun pump bushing before ever getting off jack stands, pulled trans and fixed - all seemed well..
Take to track for private track rental invite $75 ouch! Get through burnout stage and try to launch.. moved 9"s and stopped.

Well had my father and another person look under car to see if D/S was moving - they both confirmed it was not while in gear and hitting gas..

Decide to drive to Summit and buy a TCI 400 with transbrake as it was assumed I broke output shaft.
Get home with trans, start taking mine out, spin tires to move U-Joint and guess what is not moving with them!!!!!!!!!!!!!! The 9 inch broke!!!! not the trans............

Not sure what to do now....

Sorry if anyone gets bad luck from me just from reading my post, it may be contageous.

On way home from summit I spotted this bad mother on a flatbed trailer.. Just wondering if I could get that to fit somehow...

 

I find it hard to believe my luck can get any worse after the last few years but some sort of driveline failure is in the cards.

So now you have a brand new TH400 with transbrake.

I'd be interested to know what failed in the diff. My 9" isn't anything special. Factory C7AW-E case. Unknown 4.56 gears with solid pinion spacer. Non Daytona support. Strange 31 spline spool and axles. I'm abusing mine with no failures yet but I know the case and pinion support are a weak link.
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I doubt that engine would fit but I did see a 55 Chev on Ebay months ago. Drag car with a V12 Allison engine stuffed into it. Car was all painted up inside and out like a P51 Mustang. It was in Austrailia and was right hand drive. If memory serves me correct, the highest bid was $1,000,000 and it didn't reach the reserve.

 

Sorry to hear about the issues. I guess you owe the rear end gods after your 10 bolt success.

 

Isn't that ironic? The 10 bolt last and this thing breaks!

Found the culprit though! Sheared center pin...
Now, go easy and get a strong center pin or a real spool..