That OEM wire, although minimally adequate, is adequate. When you start upgrading or adding accessories that draw more current, further upgrades are req'd. IF when the 60 amp alternator is recharging a dead battery or other scenario proves the OEM wire to be inadequate, chit happens sometimes.
The simplest solution is a larger gauge wire routed directly from Alt' Batt' post directly to the battery positive terminal. This addition will instantly alleviate any worry but would bypass the ALT' gauge in your dash / renders that gauge inaccurate. All this isn't really worth the read at this point. The additional amperage this alternator could produce may never create a problem.
