Overcharging

I’m thinking of doing the MAD conversion but want to make sure the Field is getting proper readings so I don’t get a drastic over charge when I go directly to the starter relay.
It's generally a bad idea.
It puts all the loads through an extra fusible link.
It puts all the current except battery charging on a long circuitous to the main splice.
If you are going to run electric fuel pumps, EFI, a winch, then reworking the system is really needed.
If you're running a 60 amp alternator, and it came that way, then you already have a pretty robust wiring arrangement. Just find the a problem spots.
If you are or will be running a 60 amp alt, or just to avoid the bulkhead connector weakness, there are better choices.
a. One is copy the factory 60 amp alternator wiring.
b. Another, easier method, is add a parallel wire from the alternator to the ammeter.
c. Last, arguably easiest, is to add a dedicated charging wire with fusible link from the alternator to the battery. The downside is this will result in the ammeter no longer seeing the charging current because there is a shorter route to the battery. Battery discharge ( starting and running without alternator) will show on the ammter 'cause its still the shortest route to the main splice.