Chevy rims for trucks 1931 -1934 were 20in. x 5 in wide. They had a split ring to hold tire on. That was the normal production rim unless you ordered optional tires that held more weight then you could get a 20 in. x 6 in. rim. Tires are available from Cooker, Miller and other vendors just order 600 x 20 tire and tubes with angled metal valve stems. Also order flaps (gutter guards).
