1988 Chevy Silverado cold cranking

I have a 1988 chevy silverado in excellent shape except for the hard cranking in cold weather. The original engine was changed out about three years ago. The remanufactured engine has about 50,000 miles on it.I have put new spark plugs, wires, battery, fuel filter and fuel pressure regulator. Still hard to crank on cold mornings. Yes, I have even had it checked on a computer to see if it was the map sensor. Please help!