Looking for some racing advice.

[Verne_Frantz]

Darren, The single and simplest inprovment you could make for now is tires (slicks). A 105mph should be turning about 13.2 with decent traction. My prediction is that if you use slicks and reach a 13.2, you're mph will be 106.
After that, it's time to change the rear gears. A 105mph the way it is, and the way you're driving it, means the 12s are easily in reach. (but you'll have to gear it so you're using <u>all</u> of the motor)

[SmallHurst]

I am running 13.20's at 103. What am I doing wrong? 105's should be getting him into the 12's.

[Verne_Frantz]

There's no set rule to figure MPH from ET. There are a lot of variables. Generally, it's horsepower that will give you MPH. If the motor is revved past it's HP peak in the gears, it will slow down. If you're not geared to cross the end at your rpm where peak HP is, then mph will suffer, even if the ET is good. ET is "mostly" made up from how good your 60' is.
33 years ago, my '62 ran a 107 with a 13.15et. But with worse tires (period Casler cheaters) it ran 104 but with a 14.45et! The difference was being able to leave at 4800 rather than 2500. The car still made the same HP after it got going, and the small difference in MPH was because it crossed the line about 500rpm lower than before. (I was further down the track when I shifted to 2nd because of starting at a lower rpm.)

Verne