550-600HP 4spd suspension help

Unfortunately, if you really have 550-600hp, once you get some sticky tires and a prepped track you WILL break something sooner, rather than later. The Mopar 4 speeds just don't do well with that kind of power. That kind of power can get you in the mid to low 10's in a well setup car.

With that said, I would go with a good bias ply slick, get the front end travel as close to 5+ inches as possible, 90/10 shocks up front, full caltrac setup on the rear, 1 flat preload on the driver side and 2 flats on the passenger side. I'm not sure where you would want to start with the rear shock setting with a 4 speed, but if you call Calvert racing they will point you in the right direction.

Side note, be sure to have a rev limiter to protect the engine from shooting to the moon when something breaks.

Another side note, I'm not sure what you mean by "big converter cars are gutless in high gear". My car with a manual valve body 727 and an 8" converter pulls like a freight train in high gear.:dontknow: