Why wont my car start?

Ok it happened when my car stalled out in a flood, luckily no water damage was done but my engine block cracked with a fist size hole. So I got it towed home and went to pick and pull to grab a new engine block. Just my luck they didnt have a 2000 NorthStar engine in stock, but a mechanic told me to grab a 1998 NorthStar engine and we will just have to buy a gasket kit. Well we did that and now I have a 1998 northstar bottom block and all my heads and the rest stayed the 2000. Well now when trying to start it it wont turn over. Checked the codes and they read that the crankshaft sensors had a malfunction, we bought new sensors and now we are still not getting any fire. I was wondering since the 2000 engine was the year everything changed wouldnt I have to re pull the engine to change out the CrankShaft that is 1998 which is in my block