You may already know this, but just incase you don't , but as your car would of been built during August 1977 at the very latest . its now 40 years old and you can apply for the taxation class to be changed from plg to historic , and therefore not having to pay road tax as of 1st April 2018
There seems to be a bit of an issue with cars built in 77 and registered in 78 , but with a date of build certificate , it should be ok
The certificate can be got from Harvey at toyotaenthusiasts.com , who are recognised by the DVLA
II have my build date certificate and will be applying for mine when I renew my tax at the end of this month