Did you put back in the 192 or 195degF Thermostat?
Some use 180deg which lowers minimum heat level, also lowers MPG and engine oil quality, if so switch back to 192/195 t-stat
And depending on how much silicone you used on gaskets during reassembly you could have squeezed out bits being carried to the heater core and blocking tubes, back flush of core will remove those bits.
Feel heater hoses at the firewall/core, the warmer one is the IN hose, remove this hose at the engine end, point it down at the ground, or into a bucket if you want to see what comes out.
Remove the OUT hose from engine end and hold it together to a garden hose and turn on the water, lower pressure to start, then increase as you see fit.