1979 C10 temp. gauge and alternator questions.

[Rangerman]

Temp gauge in the dash works good but where does it get its reading from?

Coming out of the intake, theres a wire that runs to a temp gauge that is zip tied onto one of the master cylinder lines?? No idea why its there, but its accurate also.

Fixing to replace the alternator with a 94 amp for a 85 camaro, on the back of the alternator theres the 8 gauge wire and another 16 or 18 gauge wire that goes directly to the battery, should the small jumper wire be there?

This is a nice truck but a D.A. owned it before me.