The point of running a 13.5 motor is to go slower. The gearing is right.
If youre trying to go as fast as an 8.5 then just run an 8.5,
Gearing a 13.5 like a 17.5 is going to cause heat issues.
Now if your boosting as well... even worse idea.
I know the 44 manuals dont give gearing charts but you can get close with other vehicle gearing recommendations.
Wait... which are you saying is wrong?