I have been trying to run the heater system to find my problem but have run out of ideas.

I have an 88 4runner sr5. The rear heater works great, but the main front heater barely feels warms. I put a new thermostat in a few weeks ago when I replaced the water pump. (I figured while I was there, what was 5 bucks). Engine temp stays 190-210 ish. The other thing I noticed is after running the engine, the top of the radiator is hot, as it should be, but the bottom is COLD. I am thinking it could be clogged. Would that effect the heater as I have mentioned?

Any ideas???