years ago I used to race a 70 340 dart 4-speed, and loved it. The main issue with most of the newer units is that they use a pin and rail system to shift the forks. Manual transmissions have a interlock system so you can not engage two gears at once, because severe damage can occur. The pin and rail system makes it hard to speed shift the gears. They used to modify the pins and rails to make it easier, but I could never shift them as fast as the old mopar A-833 Put a Tremec 5 speed in a while back and paid extra money to have it modified for better shifting and could not tell much difference.