If the mount of your Altrider rear rack looks like this, then it definitely will fit.
The light upgrade fits right above the existing light and below the factory plate under the factory rack. The Altrider rack sits on spacers I believe above the factory plate.
I plan on ordering the parts this Monday, so I will probably close this batch out then.
For the rest of y'all, I still need shipping information from the following inmates:
Once I have everything, I'll PM out my PayPal info. Thanks again everyone for all the support! This has energized me to follow through with my next little goodie that I want to build.