same thing, you need the tach adapter from msd. those msd ignition tach outputs are good for nothing except high end autometer tachs and such. i dont really understand the point of them if they wont work with all tachs. but they sell and adapter to make it work with older style coil drive tachs like our cars. its gonna cost u like 30 dollars or so id imagine. even though msd says not too, ive seen people hook it up to the negative side of the coil still, although with a rally pack, i wouldnt chance it. it would be a expensive mistake if it didnt work