I assume you've done some sort of conversion? A '68 model would not have come with a regulator like the ones you show. They're for a '70-up system with a 3 wire alternator.......still not for a 100 amp alt.
It's a '75 Trailduster with a 318 from the 1968 model year. All new wiring throughout, most of it upgraded sizes. The alternator needs to support the stereo, EFI, and aftermarket A/C system.