Edelbrock Pro Flo 4 EFI

quick question: does any of you have a MSD shiflight and stock tach connected to the pro flo?. If so, where did you wire them to?, to the negative side of the coil (I have a can coil type) or to the "tach output" from the EFI computer?.
In my case I have an MSD shift light and the stock tach, I have them both connected to the negative coil side. Not really sure the stock tach will work with the pro flo tach output or not, the MSD shift light should work without issues.
Thanks for sharing your experience with this and setups used.

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