According to my Rohn catalog the bolts are as follows:
1/4 X 1 1/2" NF grade 5
5/16 X 1 1/2" NF grade 5
I used stainless on my tower but could not find NF bolts
locally. I used NC with nylon locknuts. It's been up many
years now with no problems.
73, Roger
BTW NF = national fine
NC = national coarse ( 1/4-20 and 5/16-18)