Genuine german tin is best,not mexican/brazillian or repro
Take the cylinder shrouds for example genuine ones have a deflector plate inside them to direct air over the barrels,the repro tin does not!
The fit of repro tin leaves a lot to be desired and it seems thinner steel.
Find some genuine tin,a lot of it has the vw roundel stamped on,have it blasted and painted/powder coated and it will last for years and do the job its designed to do.