yes they will choke the engine unless the build is specifically built to run them. and yes FAST class is running pretty exotic (for a 70 year car) stuff. there is a ton of money in the motors and transmissions to get them to run what they do with stock parts on them. most of the cars like i said are lightened where ever they can be lightened. places most would never think of, some run traction control, the motors are no longer 340s, they are over 400 cubes, i'll bet just the trans alone has $5K into it.