I have an XJ6 S2 3 speed auto, is there a later model auto with OD (4 speed) that will fit on my model without great drama in fitting?

 

https://www.johnscars.com/qb/xj6qb.html

 

Well, I wouldn't have said "no drama" based on this install: https://www.jaguarforums.com/forum/x...s-cars-234770/

Personally, I don't think the 700R4 is a great transmission, these days I would be going for something electronically controlled. As the OP is in Australia, I doubt that 700R4's are easy to find there. In his shoes, I'd talk to Dellow in NSW and see what they say. https://dellowconversions.com.au/