Peter,
while I don't remember whether it is the front or the rear carburettor, it mounts on the bottom studs studs of a carburettor with the short leg pointing to the inner wing, a bit of trial and error should not be too onerous?. There should be a long spring that then goes to the throttle linkage.
I just checked Martin Robey's site here:-
https://www.martinrobey.com/jaguar/clas ... r-fittings
The illustration is not quite accurate, as it shows that bracket in front of the carburettor and it seems to suggest that the spring I refered to attaches to bracket 76 which it does not (I'm not sure what that bracket is for, maybe the two drain tubes from the float cahmbers.) The spring attaches to lever 82 and the bracket you show.
Alec