Hate to say it but I hope you didn't put all fresh new coolant in yet.
Here's how I would do it.
1. Drain the radiator.
2. Disconnect top and bottom hoses from the radiator.
3. Stuff the hose in the top port of the radiator and pump water through until it comes out nice and clear at the bottom.
4. Leave the radiator disconnected.
5. Disconnect both heater hoses.
6. Using low pressure at least until you get a nice clear stream flush the radiator using the top hose or port/connection.
7. Repeat the process with the bottom heater hose.
Once you have nice clear water coming through the heater you can increase water pressure but don't get carried away. Last thing you want is to blow out the heater core.
Button it all back up. Put WATER in the radiator. Run the truck till the temp gauge reads normal, you want the t-stat to open up. Turn on the heater to full hot. You should now have nice hot heat.
Once that's all done, shut down the truck and let it cool down. Drain all that water out which should be pretty clear.
Close up the drain and put in nice fresh coolant.
I agree with Ramtech, your blower switch is likely shot. You'll need to attend to it before you can do what I've written above.
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