[blucar]

The easy way to hook up a hot water heater in a '36 w/59 AB engine is to utilize the port in the right head adjacent to the inlet into the head. Use a manual heater valve so you can turn the hot water off in the summer.
In spite of the earlier comment about the return line to the lower radiator hose being problematic, I disagree. Using the correct off-set lower hose that is sold by most aftermarket vendors, it is very easy to install the correct fitting into the hose, which is a simple,. trouble free installation.
I would also suggest that you purchase a correct after market upper hose that makes allowance for the required off-set in the radiator tubes and heads.
As you can note in the attached pix, I had the flex hoses on the 59AB engine in my '36 for many years, I know have the after market off-set hoses.