2 things, think of it as a straw your electrical system pulls from. not a hose pushing power into it.
as said above your electrical system will only draw what it needs.

can you burn something up? Yes you can, but you could have anyway.
The amps charging the battery if it were dead would be worst case other than a dead short.
if you run the amp meter bypass for charging you should be able to eliminate that issue and still keep a stock look.

second, you are probably right, if you check the parts house numbers they all probably are the same from when the square backs started to the late 80's.
I usually look for an 83 new yorker or mid 80's m body.
but find that the part number is the same all they way back to the mid 70's.
they don't need to carry 3 different alternators when 1 will bolt in and no one is going to complain about having too much power.

give it a try online and you will see the part number doesn't change.