How to test a Tach

I'm rebuilding the gauge cluster and part of that is the tachometer. Its from a 72-74 rally dash. The two main connections were a navy and tan wire. My question is can I connect it to a coil on a running car to test it? and if so where would I place the two connections?

I would go to www.mymopar.com for the colors & it needs the switched 12V to power it (blue) & the connection to the coil neg pri terminal (I ain't sayin it is the tan, check the diagrams). Yes you can test it seperately on a running engine, just connect it up with jumper wires. & it needs to be grounded.