Yes Glyn. The close up perspective in Oliver's photo fooled me. Having looked at so many, including my own long tail, I shouldn't have mistaken it.

 

Refresh page for addition of better pic. Excuse dust under build. Snipped from far larger pic so resolution not great & some barreling distortion.

 

Interesting. so I wonder which car my OD was originally in...kind of academic, I'll make it work in the XJ6....

 

I'll summarise what I believe to be true for overdrive rear casings (long tail vs short), with acknowledgements to Glyn and various spare parts books.

With the old Moss box (no synch on straight cut, wailing banshee, bottom gear) and non-compact A type overdrive, Mk2 and S type cars have the same overdrive fitted. Not many S types were built with a Moss gearbox.

With the arrival of the all synch gearbox, the original overdrives were replaced with the A type compact. Sometimes in the US, It's called a C type, but that's not the correct name. On the Mk2, the compact overdrive had a long tail. This kept the rear mounting in the same place and allows the use of the same prop shaft. I don't think any other Jaguar cars used the long tail.

In contrast, the S type, when fitted with all synch box and compact overdrive, adopted a short tail on the overdrive. I'll call it short tail, but to my eye, it looks a proportionate length as opposed to the strangely elongated tail on the Mk2. Exactly the same short tail was used on the S type, the 420, and series 1 XJ6. There are consequences for mounting positions and prop shaft lengths.

I believe that what I've written above is correct (though the logic behind it all may not be clear) for cars in OE condition. If I'm wrong, I'm very happy to be corrected. Of course, lots of cars and parts of cars have been modified over the years, so it's buyer beware and have a good look and compare with pictures on the internet.

 

For completeness, the upper photo is Glyn's short tail (from his post up the page) and the lower is my long tail. Seeing the two together makes the difference fairly clear. However, photos from difficult angles can still mislead.

 

I'll be going under the Si XJ6 with a tape measure to compare prop shaft length, rear bracket and fittings for comparison later this week. I'll take some more photos of the OD and gearbox, starting a rebuild reference album as I take it all apart.
I bought the gearbox and overdrive from Jim Griffin in South San Francisco along with a lot of other stuff when he closed up his Jaguar shop must be 12 or so years ago. Jim used to race XK120s at Laguna Seca for bay area locals who may have known him. Because I am very stupid I didn't buy the half e type he had above his doors as a shop advert or the immaculate MkII cut off front end bar decoration. Still annoyed with myself about that today, but I did buy a lot of parts and gaskets.