They are 3/8"...as for the length, I can't tell you exactly. Slide a small screwdriver in the hole with the extension on the trans, mark it & subtract a 1/4" or go to the store & grab a handfull of grade 5 3/8" bolts 1" long (too short) to 2 1/2" (too long) & use the correct ones...someday you'll be doing another project & be glad you have the extra bolts handy. Lorne
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