It is a good idea for all owners to slip a piece of cardboard between the heater and the trans tunnel. It's then easy once in a while to slide it out to check for leaks. It will pick the smallest of leaks
I have detected the slightest of leaks from the heater core. I plan to remove the heater pipes in the engine bay and delete the heater unit/core.
This is my pennuth worth. Do NOT connect the cylinder head to heater core pipe (its the input to the heater) with the heater return output pipe leading to the front of the engine (in proximity to the water pump). When your heater is set to off, hot water does not circulate through the heater core. When you switch it on then water circulates back to the front of the engine. This hot water has been cooled by the heater core, particularly if the heater blower was also going full gas. Either way, very hot water is not being recirculated back the front of the engine.
If you connect these pipes then hot cylinder head water is constantly being fed back to the water pump and the engine without being cooled by the radiator.
I will be plugging the pipe outlet at the cylinder head and at the t junction at the front of the engine. I think this is the best way forward but you'll need to make up your own mind