Gear ratios

So i have a gas rc car, and i was looking to put a little more top speed into it. The obvious way to do that is to change the gears. But i got confused along the way, and trial and error wont work here, because a single spur gear costs $10.

The gears on the 1st gear are 26 teeth for the pinion gear, and 54 teeth for for the spur. 54/26 = a gear ratio of 2.07 : 1. the gears on the 2nd gear, the one that im going to change, are 22 teeth for the pinion, 50 for spur. 50/22 = 2.27 : 1.

Common sense tells me to get a smaller spur and a bigger pinion to get more top end.

So, I'll just get this- http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXBMA4&P=7 A 48 tooth spur.

Due to gear mesh, the difference of the number of teeth of the spur and pinion of the 2nd gear must be equal with the 1st gear. So, the difference in the 1st gear is, 54 - 26 = 28. So, to get a nice gear mesh, the difference must be the same for the 2nd gear, 48 - 28 = 20. I should get a 20 tooth pinion. Like this - http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXBMC4&P=7

Am I missing something? take a look at my current gears http://img.photobucket.com/albums/v506/raysoh8/CopyofImage486.jpg

There is no way the 48t spur and 20t pinion will fit. Even though the difference is the same as the 1st gear. (28t difference) Look at the size of the black pinion, and the size of the 20t pinion! And with an even smaller spur? This is where i get confused. Can someone with more knowledge and brains help me with this. This is all new to me, everything i know is guesswork, right down to the assumption that i should get a smaller spur and a bigger pinion. And the part on how to get a gear ratio.

I think that might be backwards. First gear should be lower (higher numerically) than second. In that photo, are the larger gears on the drive axle?

I'm going to copy this to the R/C forum and maybe you'll get more responses.

Small pinion:big spur = low gear
large pinion:small spur = high gear