I may be wrong but I don't think standard Mopar aluminum 833 OD or GM cases had these gussets.............
FWIW, The MP Chassis book implies all bell housings are the same length at 7.380". Realize adding a .125" block saver plate relocates the stock pivot point rearward as well.
This input appears to have been shortened already. I wouldn't be too anxious to chop any more off of it. Once you have the bell setup you're going to use you'll have a better idea of what mod may be necessary...