You should really spend some time re grounding everything with 4 gauge welding cable
All to the battery
Alt to batt
Alt to block
Engine to batt
Frame to batt
https://youtu.be/BQdQBesuJCs Watch this video
This is how it’s done .
I run fuel injection On relay
Moroso elec water pump On relay
Massive fan puller type On relay
Elec vacuum pump On relay
Elec fuel sump On relay
130 amp 3g alt
Never an issue and I idle at 850. Charges at 14:1 all day long