Larry Hill recently completed his FS/D 392 Stock Eliminator Drag Pak Challenger. He has run 9.12 @ 145 MPH weighing 3415. Wallace says:

Your HP computed from your vehicle ET is 798.76 rear wheel HP and 887.51 flywheel HP
Your HP computed from your vehicle MPH is 731.29 rear wheel HP and 812.54 flywheel HP

This is with a stock stroke 392.

One other note is that 832 hp and 882 hp motors listed previously were with factory modified heads, not special aftermarket race heads. Pretty impressive.

I heard that MMX wasn't satisfied with the performance of the motor and car as well. I called MMX with a question once and asked for Byron. If you don't know anybody there he does all MMX's YouTube videos and is a very nice guy. He would likely give you the lowdown.