Power inverter questions

I have a 1500 watt continuous 2500 wat surge I believe power inverter. Someday want to go bigger but have had this since it was installed in my Dodge before I sold it. Looked like the po used house wire a big gauge I believe it was bigger that 4ga to power it. What gauge and wire type did you use? I was also debating whether to use a breaker or a big maxi fuse. Plan on installing it in my toolbox so it is out of the weather. Thanks

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