From what I can remember there are three types of bolt holding the pan on. I think the bolts on the corners are 5/16"-18 and the rest of the pan bolts are 1/4"-20. There are also a few stud nuts down there with the 1/4"-20 thread as well (mostly used for holding trans cooler lines up). The length is about 1/2" for all of the bolts. Good luck with it!