I've done a couple of bike carb conversions so far.
Bear in mind that a CV bike carb that has a bore of 38 mm will be 38mm at is narrowest point.
A set of 45s will typically have 36 or 38 mm chokes in so will actually only be 36 / 38 mm at its narrowest point.
Bike CVs drive really well compared to 45s. They are easier to set up and there is much less bogging when you put your foot down due to the CV design.