with the stock 4.10 or 3.9 , you will use 2nd , 3th ,& 4th rarely or never 5th.with the 4.8 or 5.12 you will use 3th , 4th , & 5th and you will get off the corners quicker. these cars/engines don't have any torque , so you have to go with RPMs . i now have a spare 5.12 so i need to will my "old" spare 4.8(ltd) in a housing with axle stubs , ready to put in a 2nd gen rx-7 . racingralph