I've taken the liberty to add a few things to make some things somewhat easier. It's been trimmed down to 5 input variables now for simplicity. Basically, you put in your RPM, your rear differential ratio, and what size tires you're planning on using (for the rear), and it'll display all the information for each transmission simultaneously, instead of having to manually edit each one, as well as your tires' circumference in feet (which is what I had the most trouble with originally). Until I figure out how to get one cell to do the job of two, the tire formula will only function for the majority of tire number formats (###millimeters/##aspect ratio/##wheel in inches)
At first, it was pretty cluttered when I changed it, but tonight, I finally decided to buckle down and fix all the issues I had caused when I edited it the first time. The result is this:

With DJ's permission, I would like to post this spreadsheet for everyone's use. Until I get his permission though, I'm afraid I can't share it, for I would feel it would be like stealing intellectual property.