Any decent custom exhaust place will weld you a new one in.
Or any EP3 after market replacement will also be ok.
My preference would be to replace the manifold and find friendly MOT tester. Many will ‘swap’ it over for beer money every year.
Manual below. It will have the classic phono input I presume. You will be able to get a phono to 3.5mm jack plug and probably some sort of Bluetooth interface.
I have the XL PS4S on the A45. The side walls are stiff but no more than the 70’s were on the DC5.
Personally I would stick with the 70’s, they looked and felt brilliant on the stock wheels.
You cannot go wrong whichever you choose, both are brilliant tyres.