Install newer alternator on 1970 GMC

[Roger 555]

I'm putting a 89 Corvette engine in 70 GMC. Old alternator had the old style voltage Regulator. My wiring diagram shows the brown wire from the old regulator to the firewall plug but diagram does not show what this wire is going to. Need to know if this brown wire is going to my amp meter? And is it still brown coming out of the harness and goes to the amp meter connection on the PC board on the dash? 2nd question the blue wire coming off of the new alternator appears to need to go to a switched 12V?