Assuming it's still on the FORD type terminals then 085 std.
If it is later or converted ROUND POST then it is 065.
There are of course heavy duty versions of each type, in the traditional ford type terminal ones the sierra/escort can be used with a 092 or 097 as a heavier one, I have the 097, Varta Blue, anywhere from £45/ish delivered to well over £150 for top range AGM.
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