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.