Hi Julian,Thank you all for your input & suggestions. My new digital 6AL is installed & fully operational. I would have liked to send the old unit back to MSD for repair but shipping costs & import duties add a lot to the repair costs so it was cheaper to source a new unit here in the UK.
The digital version offers some improvements, including a single block connector which makes it much easier to disconnect when working on the cars electrics. Also the rev limit can be indicated on the rev counter, which is a nice touch.
Out of interest where did you end up purchasing your 6AL from.