TOPIC: Tach options for 1962 Merc 500

Hello, new poster here & new to classic runabouts. I have a 1962 Merc 500 with an 8 pole stator. Without doing any research into compatibility, I've purchased an Airguide model 688 tachometer and am hoping for some advice. My field is marine electronics such as chartplotters, autopilots, etc. on cruising sailboats and I have little experience with engine instruments let alone vintage ones.

Questions:

-can I make this unit work with my engine? It has a green and a black wire and that's it.
-if not, can anyone recommend a model that will work? I'd prefer vintage or retro look.
-if I use a modern tach I understand that most have a selection for cylinders (4) and pulse. What pulse would be selected for an 8 pole stator?

I appreciate any advice someone can offer. Thanks, Brian