You use a cheap timing light on a MSD set up,not an expensive timing light.Plus you don't use the battery that is in the vehicle when checking the timing with a MSD set up,use a seperate battery to do this.Have talked to some that have done this and this is the info that was recieved.
My MAC (not looking at it right at the moment I think it is a TL 90) worked finr when I had an MSD but my buddy's S/O would not, dont remember the model he had--been too many years and neither of our timing lights were new then either
