I have an SV34 and have been all over the coach. At first I wasn't sure and then it hit me. I'm in FL and my coach is in PA so I can't confirm but I am 99.9% sure I know what they are.
They are supports for the cab running boards. There is one on each side under the fiberglass running boards around the center of the running boards.
When I was going around the under side of the coach about a year ago, I saw this support on the passenger side. One bolt was broen off and the other loose and the bracket just dangling and ready to fall off.
I am not surprised you only found one bolt. The guys that build these coaches are notorious for using screw guns at max torque such that more than half the fasteners on these coaches have been over tightened to the point the hole gets stripped or the screw becomes fatigued.
On the drivers side I found one screw missing buit the other screw was still tight.
If you crawl under the running boards, you should see the two holes in the chassis frame where the holes line up with these brackets. I recommend getting some grade 5 or 8 bolts and drilling the hole out in the frame if you have to and using nuts and lockwashers instead of the self tapiing screws they used.
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