I think it was mentioned earlier, but since your grinder can take a six inch wheel, it may have enough adjustment to tension the longer belts. If the old tape measure says it's possible, I'd try two dollars worth, and if it comfortably makes it through one rough grind, I'd go back for an arm load. If they fit your machine, but are marginal performers, then definitely pass on any more.
Just thoughts, Craig
Just thoughts, Craig