Early Midget electric Rev-counter

Maybe a dumb question but....can you calibrate an electronic speedo, as the
dial on the Frogeye speedo only goes to 6000rpm whilst the same position on
later speedos shows 7000.  Can I put in a later electronic component whilst
retaining the old dial face?
Its to go into my pre-war car as the larger dynamo won't allow the fitting
of a mechanical drive.

(Yes, I have THREE tacho drive dynamos going spare)