Well, I have a TKO tranny with a Lakewood scatter sheild.  I used 4x 5/8" bolts that are about 1" long.  I opted for the grade 8 bolts for the extra strength.  If you have some bolts laying around, find one with the correct bolt patter/size and take it up to the hardware store and find new bolts of that size.  Or even take the bell houseing up with you 
