Electrical gremlins

Good night. I have an electrical question. Ok I have a 1972 Dodge Demon. I bypassed the ammeter in a fashion similar to the MAD bypass. I've been running the car for about 2-5 months like that....Here lately I'm blowing the fuse I have in line. When I start the car and give it gas it will blow. Sometimes it doesn't. I put a volt meter on it an voltage bounces from 12.5 to 14...when I rev it to 2000 grand it goes up to 14.3 and is pretty steady there...May jump to 15. I have replaced the alternator thinking that it was shorting out...That didn't fix it. The car has MSD ignition and Fast Ez efi on it. Anyone have any ideas?