67 Barracuda Heavy Electric Load

It says use a 15 or 20 amp fuse depending on fan style , which is low. But the bottom line is the alternator is not putting out more amps than are being used at idle. Since you've already got an aftermarket cooling system you may be willing to get an aftermarket alternator that puts out what you need. Check for rpm "turn on" and amps at low rpms. Although it may be cheaper to get the proper radiator,shroud and fan assembly .