The last SBM bracket race motor I put together was several years ago.
416, Bowl blended RPM’s, easy on parts SFT, SV, 1-3/4” headers...... 561hp@6300.
Several years prior to that I had one on the dyno that I did the heads and cam for.......more head work, 1-7/8” headers, roller cam, Victor with adapter and 4500 carb......589hp.
Don’t recall where it peaked....... but was probably still in that 6300 range.
I wouldn’t expect to need to go more than 65-6700 to get one over the 600hp mark.
But......time will tell as more get built.