I've never heard of an alternator with less than a 55 amp capacity. Most of the internal-regulated 10SI models are 65 to 100 amp capacity. If you choose to use a fusible link between the dash cluster and the ammeter, it should be able to carry at least most of the alternator's output. If there's a direct wire from the alternator output terminal to the top terminal of the starter, you could use a 40 or 50 amp fuse or fuse link to the ignition switch or other junction point to the inside accessories, and an idiot light instead of an ammeter to monitor charging system performance.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!