Heater problems?

[81ChevyC10inSC]

Ok i have 81 C10 w/o AC and the i6 (250). Bought the truck some time ago and have had issues with the heater ever since. Hadnt worried about it much until the colder weather got here. The truck has what appears to be a brand new radiator. I have replaced the heater core (old one leaked) thinking that would fix my problem. It didn't. So yesterday I replaced the thermostat (195 degree) just in case and topped off the coolant. Let the truck idle to get up to temp and I had really good heat. Weird thing was only the hoses going to the heater got hot. Neither top nor bottom hose to radiator got hot.

So this morning I start it in the drive way and let it idle for 10-15 minutes. I get in a notice no real heat yet. So I drive in to work (30 minutes but only because of traffic) and still only cool air is blowing from defrost or heat. With it running I checked under the hood we I got to work and had zero leaks and all hoses are hot. I really am at a loss at this point on what to check. Could I have an air bubble maybe?

Any ideas or suggestions would be greatly appreciated