Fuel filler neck question

Hi all
Ive put a 3.5 V8 into my 90 that did have a 2.5 N/A engine in it. Do i have to put a differant filler neck on now that its a petrol as cars now days have the plastic inserto to stop fule being drained and also to stop you from putting the wrong fuel in. reason why im asking as ive still got the
Diesel tank fitted.
i have also herd of people that have made kit cars in the past have them fale the MOT as the dont have the correct insert in the filler neck.

Don't think it's a problem with a vehicle of that age. They didn't start using size specific filler necks until they stated using Catalytic Converters that could be damaged by using leaded petrol, so they used thinner nozzles and filler tubes on unleaded pumps and vehicles.

just ensure you have a vent cap