I bent the tube by holding it in a vice and tapping with a hammer. I made a small wooden jig to check the alignment of the newly bent tube. I figured it would be easier to check the alignment on my workbench than taking the heater core in and out of the car. This method worked pretty well and I was able to maintain the steel tubes in the passenger compartment.
This is the photo of the old heater core and valve in the alignment jig. You can see how I attached the firewall plate onto the jig so I could align the newly bent tube. I left the firewall plate on the jig when I removed the old core assembly.

This is the photo of the new heater core assembly in the jig.
