[Mr Gazza]

Those are the correct measurements 450 for standard Monster forks and 485 for adjustable.

Nasher put some 1098 innards into some adjustable fork tubes for me and they slot straight into the Monster yokes with no mods, Well!

The 1098 stanchions have a radial brake mount, so if you go for that particular set up you'll need a pair of radial mount calipers, new hoses, discs with 15mm offset or 4.5mm spacers to correct the offset and a longer speedo cable. The speedo gearbox is the real fly in the ointment as it just gets in the way of everything!
15mm offset discs are the best way to go, but how much do you want to change and how much do you want to spend?

Best to ask Nasher if internals with an axial type brake set up can be transplanted into the adjustable tubes. Definitely more options with the 485 tubes.
I wouldn't be surprised if the non adjustable stanchions could be fitted in the adjustable tubes along with the adjustable damping and spring.
Nasher's your man.

P.S. What hole centres are your callipers? 40 or 65mm? Good brake upgrade is to fit P4 4 pad callipers which go straight on, but do need new hoses!