The first generation Vulcan 500 has the same belt drive pulleys as the 454. The final drive is 2.72 at 6000 RPM this yields 64mph the 2nd generation vulcan 500's with chain drive have a final drive ratio of 2.625 which yields a 6krpm speed of 66mph.
You may find the spreadsheet in the 4th post in this thread useful Every japanese bike I've ridden has the speedometer reporting faster that you are actually traveling. both of mine read about 4-5mph faster than I am traveling at freeway speeds. I wonder if the 454 has different internal gearing or maybe a different size rear wheel to account for the approximate 5mph difference or who knows maybe your speedo is reading slower than you are actually going? I usually cruse on the freeway between 6 and 7K RPM. If I remember correctly both 500's redline at 10K RPM. I had a 12K tach on but switched to an 8K tach since the power band really fades on both my 500's after 8K RPM. I was going to try to get scoot works belt pulley system to work on my belt drive vulcan 500 but, scoot works has been jerking me around. Their belt drive increases the final drive to 2.22 which drops freeway rpm significantly. I sent them my pulley for testing last july or was it august. They were supposed to only have the pulley for a few days but they have yet to return my pulley and at this point I probably will never see it again.