Our B-300 was a 1971 model, single rear wheels, and we went from 8.00 bias to 8.75 radial without issue. We also had a slight rub in front, but it took some doing to get it to happen. Also, it was only a "rub" not a "scrape" making only a spot, no damage.
But if Vickie's RV is Dual Rear Wheel, got to be sure about the wheels' "offset" that produces the spacing between the sidewalls.
gOOgle search
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tires pahrump nevada
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Turned up several tire sellers, at least three new and one used. The "Big O" outfit is part of a national chain that sells under a number of brand names.
Time to wait for a status report from Vickie...
If God's Your Co-Pilot Move Over, jd
2003 Jayco Escapade 31A on 2002 Ford E450 V10 4R100 218" WB