Like everybody else said NEVER buy a CS144 without a lifetime warranty. The last 2 I got from Pep Boys were NEW alternators.
Heat is what kills them. The vette has no engine driven fan and they are bottom breathers. The early cars with the boost fan that runs off the head switch can help themselves with a lower temp switch. The factory switch turns the fan on at like 235 deg.
The other place heat comes from is the alternator trying to charge up your half dead battery.
I'm going to look for the heat sink. It can only help.
My car had an Delco alternator in it the guy had just paid $145 for 10yrs ago when I got it. The vette sat most of the year in the driveway while I was in Korea and didn't make it through one summer in Oklahoma City. The first alternator I got from Pep Boy's was rebuilt, now the lifetime warranty ones are all new.
Funny thing, I haven't put another alternator in my car since i got a battery tender. I think keeping your battery charged up will really help.
A lot of vettes sit a lot and we run the radio with the doors open and don't drive them for a month. Then when we take them out they run around town in traffic. That is really hard on the cheezy little alternators.
My old 77 impala's orginal SI alternator was in the car when I gave it away at 20yrs old. It had 2 brush assys and a diode trio. Total lifetime maintenance $15!

JS

 

Kind of interesting, how long have you been using the battery tender? I am not sure how much this effects the alternator, but I am curious...

My car is a "second" car that sits in the garage and lives for nice days and evenings for a little spin around town.

 

FWIW my local rebuilder doesn't really offer a warranty other than a DOA warranty, but they charge me $40 to rebuild an alternator, they have it ready the next day and it works better than it did OEM. Over the years I've had them rebuild several things, including the starter and generator on my dad's '46 pickup.

It's an out of the way shop downtown in a bad neighborhood, but they do the best work. Doesn't it seem like that's always the case?

 

Well, maybe I am just lucky, but I have never had an issue with either a rebuilt alternator or starter. I have put them on, and had them last for at least the next ten years, which was longer than the factory originals ever lasted. Now I know there are good rebuilts and bad, but I have always gone for the store brand Lifetime Warranty, and have never had to take one back yet.

Side story: Used to work in a parts store. Customer came in for a waterpump for a SBC. HAD to have a new one, didn't "want any of that rebuilt crap". So we ordered him a brand new AC Delco waterpump. Lasted him 2 weeks. Sold him one of our store brand rebuilts, last I knew, after 5 years, it was still going strong.

It will take a string of bad rebuilts before I spend the money for new.

My .02
DaveZ.