Any good grade 5 will work for your safety chain, I have broke far more grade 8 bolts in my life that I even remember, one thing I have found with grade 8 is yes they are strong, but on certain applications they will break before grade 5 because they are more brittle and will not give at all and will snap with the right side load. I just put new chains on my trailer and used 3/16 chain rated for 5000 pounds that I picked up at True Value and grade 5 bolts with flange heads and jam nuts, they are drilled behind the coupler into the sidewal of the frame of the trailer with the nut on the inside, bolt head on the outside.