I have always run a manual transmission car (5 speed nash) car is 3220lbs with driver. sbc (large) contemplateing going to auto. 1st question is p/g or 400?? and are there any quesses as to how much the car will slow down with the auto in it???? will I need to change rear gear ratio??? currently 4.88 car goes thru traps at 7800 with 30" tire. just trying to see if it will work . also everyone says I'll be bored with the auto ????? thoughts anyone????