Guess this mean I need a heater core

I have my slanted 6 to Magnum swap basically complete. Still working through a few issues, but it's driving.
HC1.jpg

The last couple test runs I've comeback from, I found a small puddle of coolant on the floor.
HC2.jpg


It wasn't leaking before i started the project, but way it went (two steps forward and one back the whole way) it would be par for the course.

I confirmed the hoses aren't leaking at the firewall. In fact it's all dry there.
HC3.jpg

And it's even dry on the inside.
HC4.jpg


But after getting under it, I did see a few drops where these pieces of sheet metal come together
HC5.jpg


So before I tear into it, does heater core sound correct? I can't see any coolant leaking from the cylinder head, and I did go back and apply some thread sealer on the rear header bolt, but that didn't change anything. I always figured when they go you get a wet passenger side carpet but I guess it's possible for them to leak in a way that the coolant runs outside and not inside. I guess my problem is I don't really know how it's all put together in there. But again, I'd just like a second opinion before I go through the hassle of adding more work to this already very long project.