Might be time to wire the alternator up in the old battery reference mode instead of PWM controlled via the PCM. (How To: Convert from PWM to Battery Reference)

 

I don't think this truck has a PCM controlled alternator. There are only three wires going to it: The two power wires and a 4 wire wide connector used for only one wire for the battery light. It doesn't have all the wires in the connector as it is described in the article.

 

If that's the case, then the alternator isn't up to snuff for the load you are putting on it.

 

Time for a 200A unit then if I can find one on eBay.

 

ad244 swap, search it you can normally get them out of new trucks in junkyards for next to nothing and they are known for putting out more than they are rated for. 99% of the time they only require a longer belt and bolt right in.

 

How To: High Output AD244 Alternator for ~$80 - S-10 Forum