Brain Fart ???
 

What makes for more top end, smaller pinion or larger pinion??

Larger pinion (and/or smaller Spur) make for more top end speed.

Think of a 10-speed bike for a visual

Just so you know. If you put a bigger pinion gear on it, it will decrease acceleration. You probably already knew that.

Thats an excellent way of thinking about it. Cool!!

You want the gear ratio number to get smaller to have more top end speed. Since thats the spur/pinion, making the pinion bigger makes the gear ratio smaller and car have higher top end.

Its one of those things thats seems backwards, bigger gear ratios go slower, but have better acceleration, smaller gear ratios have slower acceleration, but have higher top end.