The 8843 pump has a clockwise rotation, same as the crankshaft.
Make sure you have 'burped' the system of air. An old trick is to drill an 1/8 inch hole in the thermostat flange (position it at 12 o'clock) to allow air to be forced out while the thermostat valve is still closed.
What was your reason to change pumps? If you are changing parts to correct a problem, maybe the problem is other than the pump. And, it's rare, but not impossible, to buy a bad pump, so don't rule that out. You already changed thermostats, so we can eliminate that as the problem.
Jim
Jim Harding
#4279512 - SA452 - TKO600
#3004 - 302 - 4 speed
La Plata, Maryland