Hi Andy, yes, you need to change rear control arms to those from a F model or later. You will also need f model or later axles. There are a number of other small items, such as changing studs for the engine mount, slight modification of the metal hot air duct under the car etc. all very easy. There is a well known page online somewhere with all the details. I don't have the link to hand but I am sure someone else will be able to put it up here for you.
I am doing the same thing, alongside a total restoration and some significant engine tuning. It is very common. Have you got any photos of your car you can share?
Cheers Roger