little help and advise please on my classic p4

[400+bhp]

having failed its mot on steering and bushes and king pin and brakes, we have now replaced all the bits etc how ever had 2 re tests and it fails on the hand brake efficiency each time ?? have been told that they put it on the rollers and it should be 25% min to pass on their dials ??? is this not for the newer cars and not the classics, any views as we are starting to pull our hair out.. as a reminder mine is a 58 rover 90 p4 for the record all the brakes have new shoes and the hand brake lever feels right and is really yanked up... so many rods under the car to adjust my concern is are the mot testers trying to get the impossible from this car due to design etc etc thanks all