94 ranger wont heat up

I reciently had my 94 ranger (2.3l 5 speed) radiator flushed and new coolant added, and ever since, the temp gauge will not come up to "normal" and I have no heat, I thought that my thermostat was stuck open, so I changed it (it did have a lot of gunk on it) but did not solve the problem. Could it be that the heater core is clogged?, and would this also cause the temp to not rise? I am guessing that the sensor is located in the upper heater hose.
Any help would be great!

if the thermastat had gunk all in it, the coolant temp sensor could to, if it has gunk all over it it can cause a low temp indication, do the radiator hoses feel like they are getting hot, or are you just going off of the gauge

Well, the hoses are getting warm, at least the radiator hoses, only the upper heater hose gets warm, the lower does not, that makes me think my heater core may be clogged.

Heater cores should be flushed separately from the rest of the cooling system for best results.