Dave, That could be a safe assumption. But possibly a Powerglide-based trans on a factory built car?

Yea, trans brakes in Stock would be another step in the wrong direction. There may be more details we aren't aware of, but it's hard to imagine an engine with well over 100 more cubic inches than a 6.1 Hemi and "Unique engine calibration" being classified in Stock, unless NHRA starts them with and even more conservative HP rating than the other Drag Pack engines. But 512 cubic inches is the only engine spec we have to go on and compare with at the moment.