67 Barracuda alternator with 2 FLD connections
The test specs in the '67 service manual are not the rating.
This is snip from a '69 or '70 FSM but the point is that its a maximum load test at 1250 engine rpm, 15 Volts.
We can sometimes relate the test specs to the Chrysler alternator 'rating' by looking for the same description in other books.
This is from the dealer data book.
source:
The 1970 Hamtramck Registry Library Page (1965 - 1969)
Sometimes there is a part number for the ratings, such as service bulletin 66-78, which can be found here:
The 1970 Hamtramck Registry "1966 TSBs and Related Material Index" Page
If you got to get one from a parts store, see what they have. If they call it a 40 or 50 or 60, any one of them is probably fine. I wouldn't take one that was 'rated' over 60amps though.
I'll add that I had quite a few slant six cars and above idle speed the alternators always were able to power lights and wipers even with the heater fan on.