Hi,

I have replaced mine with a sealed battery, and as far as I am aware the new ones are made up differently, so no vent pipe needed.  As for size there are sites on the internet that give the overal measurements of the battery.  In my case I just searched for “ battery for a 1986 Jaguar XJ-SC”.  The only alteration I had to do is to file down each one of the electrodes to get a better connection.

Regards

Alan