I'm looking to buy new 12x7 and 16.5x9 wheels and R4 tires to replace the original R1 wheels and tires that came on my B7300 tractor. The new wheels and tires typically fit on a current model B2320. The front to rear ratio is within the margin but I can't confirm the 6 hole bolt spacing. Does bolt spacing change very much between similar size category Kubotas of different model years?