Constant heavy charging

Are you asking if changing the alternator will help with what you see on the ammeter?
If so, no. Still need to reroute the wiring so current isn't flowing through the bulkhead connector to the splice to the ammeter to the bulkhead, through the fusible link, hopefully through another fusible link or fuses to the new stuff.

If you don't care about having the ammeter to monitor battery charging, you have more options for wiring.
Watching the voltage can give you a reasonably good sense of how the system is doing.

Whatever you do, just make sure there is a fusible link between the battery and any non-fused circuits (except the starter itself).