Rocker arm shaft bolt size

Can anyone tell me how long the bolts should be that secure the rocker arm shafts to the head?
And are they grade 8 or grade 5? Are there two different lengths?

Small block or big block?? Small block are all the same size 2 1/16 x 3/8-16. Big block have 2 longer bolts and are also 3/8-16. I think ive seen them both suggested but since you need no more than 15/20lbs that grade 5 will work best.

Jake