Anyone think this looks like the correct heater core for a third gen? I found it on eBay and after Googling the part number it appears it should be the correct one but I don't have mine removed to compare it to for a few days.

 

Strictly from memory, that looks close. I have no photos from the exchange I made in 1999. After replacement, I switched from the silicate green coolant to DexCool and haven't touched the system since. My records show a "H6111" replacement core. That number crosses to a Stant 9083 and Vista 399083, which appears to be the number on the box in your photo.

In any case, the lower pipe needed a slight tweak on mine since the angle was a few degrees off, putting it in an impossible location for connection of the hose. I'm not sure if I damaged the core by bending the inlet pipe, since it has only been about 24 years since it was installed. Time will tell.

 

Yup, that's our heater core. If that's a new one, then great find! I'm surprised I missed it. If the seller has more, then PM me with his info. I've been salvaging them out of later generation junkyard cars because the aluminum aftermarket cores are poor replacements. One of the ones I've salvaged is actually good, but I'm still leery of installing it because there's no telling how much longer it will last.

 

I would also recommend getting rid of all the green antifreeze. Dexcool is a little old. The newer red or yellow antifreeze is the way to go now and they're backward compatible so if you still have a little bit of green AF still in the block, you don't need to do a full flush to get it all out.

 

American green antifreeze is perfect for cooling systems with mixed metals of iron, aluminum, and brass. And it forms a protective barrier much faster than Dex Cool -- important for cars that aren't driven much, or cooling systems that are opened up regularly for engine mods.

Keep the green. I run it in my LS7 car too because of my brass radiator.