Does size matter ?.

[rchippie]

Now that i have your attention .

My ? is about spur gear size inrelation to pinion size . To get the ratio i need i have to use a 66t or 60t spur with a larger pinion . The car comes stock with a 72t spur . I cant use the 72t spur & get the ratio i need . So how does the size of the pinion in relation to the size of the spur affect torque & top end ?.