Hi, I'm looking for a relay that can handle 6 gauge wire, it must be for 120v 75-100 amp,and be triggered by a 120v signal. I have a garage a ways down from the house and I'm trying to see if there's an alternate method from the manual power transfer switch box. This way all I have to do is flip a switch and the garage is powered.

You are looking for a contactor, not a relay.

#6 wire is only good for 55 to 65 amps, you plan to use this for 75-100 amps?

Are you sure you this is what you want to do?

A contactor in the 100 amp range is not cheap:
Electrical > Starters and Contactors > Magnetic Contactors > Contactor,NEMA Size 3 : Grainger Industrial Supply

There are other brands and other distributors, price may be close to this.

Sorry, it's @ 50 amps, I guess I went crazy with that number.

My question is why do you need to turn the garage off, and if you do why not just flip the breaker?

After re-reading the question:

alternate method from the manual power transfer switch box.

Looks like an you want an automatic transfer switch?

Get back with better details of what your planning.