don't buy an alt bigger than the amp wires would handle. non ac will be factory around 35/45 amps. You can install 60 and 65 amp ones on there, but if you go bigger, you need the propper wire size to carry the amp load. Or it will get hot, melt the wire coating and do a lot of damage. May even catch the car on fire. I run my 70 bh car with no ac with a 45 amp. No issues. But big radios need big amps, so be careful. Also remember that all those amps go through your steering column. And will burn the plug splice connector as well. Along with the turn signal switch.
Stay within your margins. Good brand rebuilts over the counter for the most part do last. Stay away from things like home of the lifetime warranty.