Hi Uncle D,
I fitted Overlander mufflers and exhausts on my 1966 Lilac 500 flat twin about 20 years ago. I gave Barry old ones to copy. He did them all in stainless, but chrome plated the exhaust pipes, as he said they go yellow from the heat. The mufflers tended to yellow slightly where they fit the exhaust pipes but polished easily.
The bike is in storage now, but I know I will never have to replace them.
Cheap at A$824.
And yeah the modern blinkers were a cool idea at the time. I have now got some bullet-shaped ones from Paul Goff, but not yet fitted.
Colin