Hi Underdogbiograd,
I don’t think you’ll get credible data on what you’re looking for. GPA data is in fact scarcer than GMAT data. On GMAT, you would at least see the middle 80 percent range at most programs, but less so for GPA. So it’ll be hard to find where GPA bottoms out for different programs.
Having said that, you should focus on what’s in your hand. If you’ve any reason(s) for the poor GPA, explain it. A high GMAT score can offset poor GPA to some extent, but the best insurance would be some solid professional trajectory or coveted industries or marquee names. The few outliers who get into top programs despite outlier academic stats usually have some solid professional credentials.
Last, if schools like you, it’s easier for most of them to accommodate a poor GPA than poor GMAT. It carries lesser weight in most rankings and if your GPA happens to be on non-4 scale, it will likely not be reported on the school website as well (most schools are silent on the methodology they follow, but few, including HBS, disclose this).