Electric Woes

I've been trying to fix this electric problem for a while now. I had recently gotten a 100 amp alternator because my old 65 amp had failed and I have a few things that demand more electricity in the car. Well, for some reason recently, the maxifuse I had installed to bypass the fusable link had kept blowing on me. Thinking it may have been something with the alternator, a friend allowed me to borrow a 65 amp alternator to test it, I had also replaced the voltage regulator at this time as well. What happens? The fuse blows again! So I'm wondering, I'm using a 30A fuse in the bypass...I've heard of people using a 50A fuse...should I try that? After the fuse blows the dash gets bright for a second and then the voltage gauge goes up to 16+ volts (the needle goes back and forth rapidly) and the ammeter goes dead...as it just stays suspended usually in the middle. I assessed the wiring thinking something may have burned but had found nothing. Should I put in a bigger fuse? Could this be something else? This only happens while I drive and the rpms increase, it doesn't blow at idle.

Thanks!
Craig