[padredw]

That 60' you speak of is 120V AC. Very little in the way of voltage drop.
So insignificant, it doesn't even matter.

If it were the 12V DC traveling 60' then it absolutely does become a problem.

This is correct. You may want to review my post above. My experience is that the power FROM the inverter is AC not DC so very little loss from line. I use the regular 30 AMP cord just as I would from a campground pedistal. 30 AM because that is the way I had mine wired