[Blacdout96]

i would do the old boiling pot of water trick. take out your thermostat, and drop it in a pot of boiling water, see if she's opening up. also as LT said, the SBC and LT are different.

Worst case scenerio, could have intake or head gaskets that went bad. check your oil/coolant, see if there's any oil in the coolant, or the oil is tan.