I got another alternator bigger amps will put it sometime this week
You should clean the contacts in the connector and you should clean the connections on the charge wire, battery , junction post on firewall, and you should clean the grounds as well as the bracket where it meets the alternator case. I’d even say replace the charge wire and go to a larger gauge as well.
Resistance reduces the ability of the system wiring to supply the truck it’s power needs and if I recall right the system senses voltage at the junction. If so, that means that the alternator has to put out a lot more than necessary to keep that voltage up when under load.
The si alternators are not like newer ones which have provisions to start upping output slower and gently (not all newer applications but most)
Also how small of a pulley is there on this unit relative to the crank and wp