The Chinese Delco clones can be had right now new for $69 delivered including warranty. That pricing is so low that I don’t dabble in it anymore, unless somebody wants high output or genuine Delco. 70A is plenty for these trucks, even with aftermarket accessories. And, the Chinese units seem to be holding up fine. Actually, the genuine Delco that I am benchmarking which I paid $330 for at a truck dealer failed in less than a year of hobby use, with new batteries and no accessory loads. This is the alt in my avatar, had to solder in a new regulator already.
Correct bracket available for 8.3L available from Cummins ($100), weld an additional ear onto the 250 bracket. Pulley $18 on eBay. I don’t give links or part numbers to the $69 one, as I don’t want to field calls for “It doesn’t fit.”, or “How do you wire it up?” at that price level.
Thinking about offering it as a kit with support for $100 cost adder, or just doing a write up and post an article. That alternator really only needs the + battery wire and case ground only, connected. Tape back the small 2 wires in the truck harness.
You can also really make it simple and just run a new B+ wire from the alternator to the back of the starter, and abandon the truck harness for it. That is how most of todays new semi trucks are wired, for the main alternator cable anyway. There is the $100 support, for free.
Even the Chinese clones are decades ahead in design over the stock mil unit. They will not over-volt on an improper switch shut down order, and wipe out your ABS, CTIS, and/or PCB.