Speedo and Tach replacements

[Rollin668]

I'm considering ditching the stock Speedo/Tach set-up and mounting one from a different bike.  I'm wondering if Tachs/Speedos are luniversal to an extent (obviously I'd like to steer clear of electronic tachs/speedos), but is there any conversion that needs to happen in the front wheel to make sure this new speedo is accurate as well as the tach...

Anyone mount a different set-up and how'd it go?
I'm aware that I'd need a new bracket but that's fine...

Thanks.


Rolly