Well I looked at alot of props and called alot of prop shops and they all said to go with the same pitch that I had or real close to it. Yamaha makes a 18 and a 20 pitch SS prop. I didn't want to jump from 21 all the way to 18 so I compromised with the 20 pitch. Plus I found a steal of a deal on it. Also when I looked up the Solas 19 pitch prop like the one you got they said it was the same as the 20 pitch yamaha that I bought. So that made my decision a little easier. See info below.

3 13 1/4 19 L 3442-133-19 SOLAS 3 13 1/4 20 L MAR-GYT3B-L4-20 Yamaha

SBC - They only make the 12 5/8 in aluminum. Check out this sheet below. It shows the props that yamaha makes and the diameters.
http://www.yamaha-motor.com/outboard...20T50~F115.pdf

DoubleG