A bit past chilly these days in Tennessee, and don't want DHS called with me taking the little ones to school with no heat...Heat exchanger was leaking, and motor blown. Hoses were not even attached. So time for a rebuild.
I did the vinegar soak in a big Walmart tub, took 5 days and nicely ate the rust off the heater box. Don't put the middle piece in, or not in for long...don't ask me how I know, but it's not all steel and vinegar will eat more than the rust away. So I had to contact Tony at 4-5-6 trucks and he shipped me a replacement for $45, and in a rush so I had it for Thanksgiving weekend to rebuild.
Here are the parts soaked, cleaned, primed, and painted:
Used some gasket material I bought at Autozone for the gaskets:
Oldest boy helped me put it together.
Replacement motor and fan from LMC.