273 overheating after new timing chain set and waterpump

Dont trade your pump in as a core. Hang onto it. I bought a new pump for our 67 cuda 273 and the machined bosses for pwr steering pump and alternator were off. I kept my original and have since found an NOS one.
Your old one may come in handy for measuring etc. Rebuild kit?
I'm trying to find a rebuild kit but no luck yet. And I get what you're saying, I really don't want to let the old one out of my sight. The new one was an actual new one not a rebuild so I was able to keep my old one. Thanks for your post, Wally