where to hook up the tach? Mallory and MSD stuff

[oldfox]

Hi, I'm gathering stuff up for my fox and I may have ran into a slight snag.
I'm going to run a supercharger with a carburettor set up I'm going to run a Mallory distributor with a blaster coil and a series 6 MSD-BTM box to pull back the timing when under boost I would like to keep the stock tach but somewhere I read that you should not hook up to the negative side of the coil or damage may occur to the module in the distributor. My MSD BOX does not have a place to hook up a tach. Anyone run into this problem?

I'm running a kenne bell right now with the stock distributor and the MSD Box and the stock tach works fine.
I tried to call Mallory and there number has been changed-nuts-

 

[HISSIN50]

The stock tach should be fine. It grabs the signal before the coil, so the box doesn't affect it. If you rewired the stock tach or added an aftermarket tach, problems could arise.

If you need to connect a tach, you could try it on the body-harness side (the wiring before it goes through the box).