Need to upgrade 68 Cuda alternator to high amperage

25 amps for ac operation may be low. I dont know what kind of draw their blower motor creates. but at the same time you need to supply adiquate current to the compumper drive clutch or it will slip and fail prematurely. Remember that clutch will energize and try to match any engine rpm instantly.
Also anytime the a/c is running those radiator fans will be running. Their amp draw will vary with resistance to air flow/CFM. Add a/c condenser and trans cooler to radiator and you can count on being near their peek load.
New vehicles have 100 amp plus available so you can turn every item on at once.
If I had to choose between a 'denso unit off a Honda ( has a fan ), and a late model Chry' unit ( has more holes shot through it that the typical sponge ), give me the denso.
Just my opinion.