[FlyingGumby]

Bolt head says 48 which I assume means 4.8. I think it's an M10 which implies 18 ft-lb max torque. That's not a very strong bolt.

Closest metric fit would be M10x30mm. It was suggested to go to 10.9 or 12.9 which implies 55 ft-lb or 63 ft-lb max torque. Does this match your charts?

I'm motivated to prep the brackets and ask a friend tack in some new bolts.

Thanks.