72 Slant Six running too cold

Too cold? hahaha, Mine runs right where yours does, doesn't matter if it's 40 or 90 outside...
When I first got my car it had NO heat at all.. I started replacing things, but it ended up being the outlet from the water pump was clogged with corrosion. Even now after replacing everything except the heater core ( it flows nicely with a garden hose hooked up ) the heat wont ever get "hot" unless I run it hard.