Heater Box

Odd story here. I just purchased the car a few months ago. The only spare part it came with was a heater box assembly. When I removed the installed heater box, I found the rear cover badly damaged and badly repaired, so I turned to the spare assembly for the rear half, which as I have noted above is distorted, so I'm zero for two so far!

The installed heater core has a date tag of 1988, and looks new, with no signs of leakage. It won't hold a vacuum however, so I plan to take it in to a shop for a leak check.

The housing halves are quite fragile, but I haven't broken them. I'll take care upon reassembly.

Thanks for your response.
Was it together before you took it apart?
Yes, both boxes were assembled, but both had sealant on the mating surfaces, so both had be apart previously. I didn't take note of how well they had mated before I disassembled them.