Hi Graham,
My 900ssie forks fit straight onto my 600ss as do the 620s ones, 620 monster ones, 750ssie too.... Try to find a set of 900ssie forks, there probably the best option and get them serviced with new oil & seals if needed, thats all I did to my 600ss ones on the race bike and they're really good, although we cant use the 900 adjustables
Andy