When they stopped me ( I was not speeding or doing anything wrong ) the cop looked over my car and said "this doesnt look like a standard Capri to me I am going to do some checking " He went to the boot of his car and came back with a massive book which had all different makes and models of cars specifications in it. He also had a tape measure and one of the things he did was measured the wheel track front and back. " Too wide as I thought" he said while looking at the Capris standard factory specification.The 4 barrel Holley carb was also picked up plus the steering wheel was to small and the suspension was lower than it should have been and lots of other things.
Luckily I had some mates who also had V6 Capris and lots of spares so we managed to swap everything back to standard so when I took it to the Police Garage it passed and the defect notice was removed.
I then put everything back to how it was and never got stopped again!! I sold the car later with all the modifications but dont know if the new owner ever had any problems with the cops.
That is one good thing here ,you can modify your car as much as you like and providing it passes the M.O.T. no worries. I declare all the modifications done to my 2wd Sapphire to my Insurance Company and also have an agreed value of £21,000 on it so if it was stolen or written off at least I would have enough to buy another good one!