I went through this last year, and it was quite painful. I use a single cable that pulls both parking brake levers towards the center of the differential, and it works very well. I use a Fiat 127 parking brake lever with a single cable. The key to getting the Jag parking brake working is adjusting the ratchet mechanism. I fiddled with a nonfunctional parking brake for months, until I read a great article on fixing each caliper's ratchet mechanism. The cable passes through the RH lever and terminates on the left.
