Hi Guys (and gals) new to this site. Hey I'm an old wrench from the 60's era (the real Dodge Hemi's 426's etc) I've got this 98" concorde 2.7 ci thats got the no-heat or very little heat problem. In a way I suspect the theromostat. the engine takes 20-30 minutes to heat up to get the gauge to move the idiot dial up 1/2 way between cold and hot. The anti freeze level is up to snuff. I did replace the water by pass jacket unit thats located up front on top of engine in front and in center(like where old thermostats used to be). I don't believe that there is air in the line. In this modern day crap of computers and sensors etc I'm lost.Give me back the old days. I guess my question is:
1. Is it the thermostat and where the hell is it located?
2. Or is it a mixing valve, maybe the temp dial on the dash
3. Or is there a valve or something that is not opening. Thanks for any help.
4. My low speed resistor for the heater blower is blown as well but should not affect this.

PS I can still put an old hemi together with my eyes closed(had 8 of them) Thanks for any help Big whit