Just a warning to anyone trying to get their vehicles changed to Historic Vehicle Class and obtain a tax disc. I sent all the necessary documentation to the DVLA on the 22nd April 2014. I also had to prove that the car was built in 1973 - even though it was not registered until February 1974. Despite various emails to the DVLA - it was not until 8th May 2014 that the site showed that the class had been changed to Historic - to date (11th May ) I still haven;t received the tax disc!!! This is despite the fact that the site is showing is being taxed from 1st May - I had originally requested the disc to start 1st April !!
My advice is to make sure that you send all the necessary documents well in advance of the 1st April - this will apply again next year when any vehicle built in 1974 will change to Historic Class