95badboy

First ls1 fbody. I judo purchased it two days ago and am having issues with it. I went to replace the tstat and there was not one in it and noticed when revving the engine it pushes out the top of the radiator cap. I tried three caps already. I was told its a new radiator. I dont know anything about cooling issues and i was told that if they mixed the dex cool with the regular green antifreeze that could be the cause(auto parts store employee) please help that's all the info I have iv had the car two days