I did a minimal pressure check on the heater core. I filled a sink deep enough to submerge the heater core but not the inlet/outlet points. I then put ~10 psi air pressure on the heater core while it was submerged. I looked for air bubbles and after about 10 minutes, didn't see any and decided(hoped) the heater core was good.
I did a little more assembling of the heater box components. I installed the two door mechanisms and installed the remaining seals.
I thought I would let those seals dry and then put the heater box back together tomorrow.
