Years ago i bought a 72 Challenger as a roller and dropped my street 440 and 727 into it. Unbeknownst to me , the car had a power brake master cylinder pushrod with a manual mc. There was no brake light switch either, so nothing to keep the rod from coming out,which it did on my first pass. What a surprise to find the brake pedal up against the bottom of the dash when it came time to stop. A downshift to 2nd didn't help much, so i went to reverse. I thought i could just bump reverse and put it back into neutral. Locked up the slicks and pitched the car sideways pretty good. Instantly. Can't say i wouldn't do it again but it would probably be a last resort. Im sure i was well below 100 mph when i thought to put it into reverse. Hate to think what would happen at high speed.