Hi Shemozzle, Your between rock & hard spot here....
New repro Lucas
$50-65. I have no idea what silvering costs.
I just ran into a dull reflector recently. Rather than like chrome, it was more like bright to dull silver. So obviously tarnished. Some rust(??) looking stuff showing through. I'm wondering if this headlight was left open in rain & it got water in & sat until it evaporated.
I put cut up piece of wet t-shirt fabric stuffed through reflector hole. I wetted with distilled water. Shook it all around well. Cleaned glass fairly well. The silver was only very slightly better. Dirt & some silver chips came out on rag. I put dry cloth in to dry it. I did this 3 times. Not being bright silver reduces light out put a fair amount.
I cleaned my own head light same way. Silvering was perfect, but what I'll call a little dusty. The dust stuck to rag. Dried it as above. Set in sun to fully dry. Came out perfectly. As it wasn't bad the improvement in light was minimal. No silver came out, nothing bad happened. It looks like new to my eyes.
Here's another aspect. It depends on what you want for lens. The original lens pattern & Lucas
Logo is no longer made so far as I can tell. It would depend on exactly what you have now of course. But if it must look original, re silvering would be desirable.
I guess it would depend on what you have now, the repro ones seem to shine on road similar to the originals, even though glass looks different.
My hunch is if your silvering looks bright & solid, just dusty it will survive cleaning well. The one above that lost some silver I could see through the lens enough to tell the silvering was delaminating in places. I expected it would loose silver. The glass was quite dirty, it cleaned up well.
My experience is if the silvering is "tarnished/dull, it's junk. Until you attempt cleaning, might be hard to tell if dull or dirty. Keep us posted on your results.