454 overheating possibly?

[68black_betty]

my 454 is will not cool down according to my temp guage, it started about a week ago, letting it idle to warm up usually it hits 190 and the themrostat pops but lately it would just continue to heat up until i started driving it then it would go back down to 190, that was about a week ago, over the last few days it would heat up even after the thermostat popped but it would bounce back and forth from about 220 to 240, i replaced the thermostat and its still doing it, im gonna go pick up a temp gun today to see if the engine is really overheating or my gauge is just went out, but a bigger question of mine is before this all started happening, as soon as the thermostat popped it would kick out hot air with the heat on, bout a week ago it would hit 230 as i said but the heat wouldnt come on til you started driving, it would just be kicking out cold air, has anybody haerd of this or had that happen to them, im not losing coolant at all, and its not really burning oil anymore than a normal big block