2004 Chevrolet Caprice engine heat up

Hello.

i have a caprice 2004 LS bought it second hand last year and god the engine changed. The replaced engine (second hand) had a 75,000km run on it. At first I had engine heat up problem in it but that was fixed by taking off the thermostat. I live in United Arab Emirates, and the heat really gets under the skin here. Well the time I changed my engine it was winters, now in the summers my engine stays cool in the night but day time the temp rises almost to the red line. :( I flushed my radiator and engine and filled it with coolant, yet I am still facing the same problem and when ever I drive fast the level rises where it doesn't happen in other caprice on the same model. Checked the water pump too its working all fine. The new engine that I got is American specs engine. And the one I had b4 was gulf spec engine. Please suggest me what should I do. And there is always heat coming from my dash board (maybe engine heat from the front glass vents) my previous engine run was 2, 60,000km and the new one 90,000km.