1989 Chevy Blazer water pump rotation

I recently purchased an '89 chevy s-blazer with the 4.3 L V-6. I live in a high elavation colder climate and as it has gotten colder I noticed the truck wasn't putting out very much heat. So the first thing I thought was to replace the thermostat. When going to replace it I found there wasn't one in there. When I put one in, the engine will overheat. To make a long story shorter, I ended up replacing the radiator cap, upper and lower hoses, radiator ( new ), and water pump. After none of this stopped the overheating, I tested the thermostat and found that two I had puchased didn't open but the third did. This didn't stop the overheating. I took the water pump apart to check rotation to the pulley and found it is turning in the wrong direction. This is the pump direction ( reverse ) that is used through '95. I tried to use a newer pump ( clockwise) but It is to different to mount. I'm not sure what if any modifications were done to this engine. After $200.00 + I'm running out of ideas as to why the pump is running the wrong direction. Living in the high country I would like to have heat without overheating the engine. Note: The cooling system was also back flushed before the new radiator.
The truck will run cool without the thermostat, as it was when I bought it, but this is with low heat, poor milelage, less passing and climbing power, etc.
Bottom line: Why doesn't engine rotation corrispond to the water pump.