Disclaimer: I researched this on the net and I'm happy with the results. Just don't blame me if there's an issue! Basically I looked up various p/n from different websites, went to the manufacturers websites and started looking for alternate temperatures. The XJR unit is not magical or complicated or special. The standard temp is 183 F it seems. Mine had a 190 in it and ran a bit hotter than I'd like.
Today I installed a Gates 33078. This is sometimes shown as a 180 on some sites, but it is stamped 174. My car now runs at 190 on the road and 195 in traffic. The 33078 is equivalent to the Stant 13648. If you want something hotter, try the Gates 33079 and Stant 13649, at 190 F.
The flange fits the car perfectly, keeping in mind you need the Jag seal, which wraps around the flange. To be extra sure, I measured from the flange to the port where the coolant exits the block. I then boiled both units and confirmed that the thermostat extends far enough to block off the port as designed, to send the coolant through the radiator.
Hopefully this info will help.

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BTW, these units have the jiggle pin, to allow air to bleed through the valve. [IMG][/IMG]

 

Don't suppose Waxstat was stamped in the metal?

Last time I ordered a Gates, it came in a Napa box and was stamped Waxstat.

Not entirely bad since Waxstat is the original fitment.

BTW, found this in my notes under thermostat for the fan hysterisis:

fan settings:

96C on, 91C off
205F on, 195F off

 

No there was no branding at all. The only information was China stamped on it.

 

So are you happy with those temps?

 

I'd say so. It was 203-210 in traffic and AC on a hot day. Today it's rainy and 19C, but still, I think 190ish is pretty good. The thermostat is so easy to change on this car if I felt like going back higher.
So now that the temps are good, and there's no leaks, I drained it, and refilled with distilled water and coolant, and now I can move on to other tasks.

 

Look,

Here is one for only 99c+ $4 shipping

Gates 180° Themostat 33078 | eBay

 

You can tell it's pretty old, not only by the box, but by the fact it was made in Germany, not China!