Factory bell housing bolts?

Most of the bolts that go from the trans side into the block are 3/8" coarse thread about 1 1/2" long for automatic bell housing - adjust length as needed for your application...

Then there a couple at the bottom that are 7/16" coarse thread that go in from the front through the block and thread into the trans on the bottom sides.... Not sure of the length for those but I would guess about 1 1/2" - 2"....

You can get some grade 5 or grade 8 bolts from your local hardware or home improvement store...