Fusible link?

I have a 71 Duster with a 318 V8 in it. When I first started working on the electrical system the fusible link blew. Lots of smoke and stink.
It is connected to bulkhead connector 'J', which directly connects the alternator to the ammeter.

As I had not idea where to get a replacement part, I replaced the wire fuse with an actual fuse. I had no idea what the amperage was/is so I asked the guy at the parts store. He said that he would think 15 or 20 amp fuses would be enough. It wasn't.
I put in a 30amp fuse, which has blown many times, usually my own fault. But a couple times, today being one of them, the fuse will pop in the middle of the road at 40 mph.
I have been working on the electrical the last couple days, so maybe I weakened it.
My question is, What Ampere rating should the fusible link be???
I am hesitant to go over 30 without some verification.

Thank you in advance for any information you can provide

Ed