I don't know enough about breakage tolerances and metal grades for this unit to match them up properly. Do you have those number? I have just had to replace one gearbox because of the wrong bolts that resulted in a damaged brass gear.
The shear bolts for my Honda SB1013B are, as per Honda specs, as follows:
On the auger - 5/16" x 2" (grade 5)
On the driveshaft into the reduction box from the fan, it specifies the same bolt. However, that particular bolt has a groove, near the head, machined into it.
www.okcpropower.com still stocks many parts for the SB1013B. I can't imagine the shear bolts will be very different, if at all, between the SB1013B and the SB800. Call 'em up, ask for Kyle or Les in the Parts department, and tell 'em "John from New York" sent you.