Alternator install/Charge Wire Questions

Hello all, I'm reaching out to ask a few things about an alternator upgrade that I'm doing to my '71 Swinger. I've decided on getting this Powermaster 95 amp unit to future-proof the car for upgrades and improving the charging system. My car has a 360 small block and is non-ac with a dual-field externally regulated alternator currently.

Powermaster 7519 Powermaster Retro Alternators | Summit Racing

When installing the new alternator, I've read that it's best to add a new charge wire with a fusible link running from ALT to the BAT terminal on the starter relay. What gauge wire/fuse link is going to be best for doing this? And will the existing wire from ALT running to the amp gauge be okay to stay connected? I'm trying to avoid causing any safety issues during this install and would prefer to not have to take out the gauge cluster. Additionally, I think that the MAD bypass method does something similar to this to bypass the bulkhead connector block. Is that basically what I will be doing, just with a thicker gauge wire?