Low engine temps

The thermostat is a 195, thought maybe it was stuck open so replaced it. Running a 50/50 mix on the antifreeze. The engine specs are a 318, stock bore, 5.2 magnum heads, comp 256 cam, air gap manifold and holley 4160 carb. The radiator is a 26" from I think an 87 Diplomat with a 7 blade fan on a viscous clutch with a shroud. Timing is set to about 8 degrees at around 900 RPM, but I don't know the total timing and when it's all in.

The aftermarket guage, a cheap Equus electrical sender reads 160-160 whether stop and go traffic or highway driving. The factory gauge runs between a third and a half, and the air coming out of the heater core is lukewarm at best, by no means as warm as it should be.

Hope this additional info helps, any and all ideas and suggestions are appreciated.