Hi to all.
For what can worth my experience, in these days i'm in progress with the substitution of my 1998 VFR 800 front fork with parts coming from a 1995 CBR 600.
Is a simple work why is possible the tubes substitution only, maintaining the original VFR external case, that means no CBS brake system modification.
With just same kind of work required for the fork seals substitution, installing the CBR tubes you will have the useful compression setting on the fork taps and a longer spring setting.
The mod will be completed by a linear spring rate kit instead the progressive OEM equipment.
All parts dimensions are parfectly the same except for the tubes lenght (CBR's are bit longer than VFR's), but this just means a different ledge from the upper triple.
This is an entry-level conversion kind; obviously a front end swap with an upside-down fork can be much performing, but much more expensive, because if your idea is an USD fork, is better to choose a full setting model and not a simple "inverted" fork with no possibilities of settings.
Ciao, Luigi.