Dash Gauge Cluster Question 71 Blazer K5

[BlazerBoy]

I have a 71 Blazer K5 and it does not have a factory tach but i found a factory cluster with not only a tach but a "Air Pressure Gauge" I have no idea how that would work at all or what it does or even if it can be connected to my rig? So the 2 questions i have are is it easy to wire up the factory tach and could the "Air Pressure Gauge" work with my rig and how would it work and what does it do exactly LOL?

Thank you very much in advance for all of your help and i look forward to being a member of this forum

Shaun A