It looks like someone may have painted over the nomenclature on your alt, I believe the reg you are looking for is a AMA2004AS.
On some alternators it is reported that the outside circumference must be filed down a little bit so the regulator will slip into the back of the alternator.
Also your alternator likely has three leads going to the regulator and the replacement has 4 terminals, you simply do not use the terminal that does not match the leads from the alternator, when you open it up be careful and take several pictures before removing the leads from the old regulator.
Many times the wires are damaged where they connect to the terminals and the tags that have the wire ID is damaged so you need to pay close attention to where all the leads were connected.
THIS is another reason to rebuild the 60A as soon as it starts to act up, the longer you wait the more damage is done to the wiring etc.
For all the reasons above I highly recommend removing the alt and build it on the bench, if all things were perfect you could do it on the truck but it is much more difficult.
I have had pretty good results dealing with these guys and they have notes on where the wires go.
Regulator assembly for the Prestolite AMA5104UT / 10929868 and AMA5103UT 60 Amp, 28 Volt alternator used on many Military vehicles. Regulator P/N AMA2004AS. Alternate p/n 35-605, 35-790, 5730138, SAW-11808666. NSN 2920011808666. Made in USA. 2 lb <hr> Notes: <u>Will not fit 10929868...
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