Dvsa dont really like issuing Q plate these days unless they have to as it has ramifications when comes to Mot time
As for mot you have to treat the car as if it was built before Aug 75 for emissions and Jan 71 for rest of test.
Which could mean that a number of components on the vehicle that should be tested dont as it was not compulsory at the criteria applied to the set down age limits.
For example before 1st Apr 86 cars dont need side repeaters or a hazard switch.
Also age related changes to seatbelt rules and other items.
So these days whenever possible Dvla will try and issue an age related plate
To make sure any applicable vehicles are tested to the correct standards.
Stephen.