Hi I have a Jaguar S Type 1964 3.8 and having trouble sourcing a fog light, I'm told I need part number C21731, any idea where I can get this or an alternative?
Many thanks for you help in advance

 

do you want the ones that fit in the buckets where the "horn grilles" are? ( there were never any "horns" fitted there).
I have a pair of those S type fog lamps in my website:
https://classicstypeparts.webstarts.com

if you want the rectangular ones that are bolted under the front bumper, you can get those from any manufacturer like Bosch, Hella, etc.

Note that the S type has larger buckets than the MK-2, so it was designed for larger fog lamps, 5.25" inch diameter.
The MK-2 "FOG RANGERS" are too small for the S type, measuring 4.25" inch diameter.

 

The S Type takes Lucas FT6 LR fog lights as does the Rover P5. Watch Ebay. They come up from time to time. The sealed beam they take is common to many Lucas bumper & rear mount models. You might have to toss out some casings to achieve a pair of working sealed beams. Mazda lighting were the last to manufacture them for Lucas. The Lucas Logo varied slightly over the years with number of vertical lines changing around the word Lucas. Try & find a matching pair. The FT 6 was vertical left top on early ones. It ultimately became larger & centre bottom above the sealed beam "Made in England".

 

As Jose has stated if you are looking for the front fog lights you will need the Lucas FT6 LR sealed beam units which are 5 1/4 inch. Unfortunately for you Lucas no longer make them so you cannot buy them new. If you search ebay you might find some and if you look hard at auto jumbles you might find some on a table but check they work before buying. They were used in some free standing Lucas pathfinder fog lights which would come with the stainless steel surrounds for bolting to the bumper but as you just need the bulb either flog the stainless steel without the bulb or throw them away. This is one on Ebay with the correct FT6 sealed beam https://www.ebay.co.uk/itm/184933084...IAAOSwX2Ng6KMw
I have several bulbs which I have found at auto jumbles as spares in the attic so if you find some buy them and store them somewhere safe.

 

Yes Rob. I have a number of working matched pairs. I also have a brand new pair that I ordered 30 years ago that I guard with my life that include the front Chrome surround & screw.