Right now I have no tach signal as the supposed "green" wire off the bigstuff doesn't seem to exist according to the instruction manual. Has anyone used the signal off the MSD box to their stock tach before?
On the 87-93 you don't need anything but the MSD box. I use the MSD 6AL and there is a female terminal that is set into the box. Just put a male spade on your tach's input lead and you should be good to go. I have a 93 GT fwiw.