good place to grab power for tach?

[blackmopar]

putting an aftermarket tach in the 64 with an HEI conversion. Red lead (has its own inline fuse) needs to grab a switched 12v lead.

Anybody know if I can splice into the Pink wire that goes from Ign Switch to the Bat terminal of the HEI? Would that cause signal interference?

or is it better to home run it back to the fuse panel? If so, any idea which terminal to run it to? I currently dont have wiring done or battery in the truck so I cant physcially trace a switched 'Hot'.

Thanks