So I am putting a new crank gasket, water pump and timing stuff. The timing gear and harmonic balancer had to come off with pullers, they were stuck on there like crazy. Now they won't go back on and the end of the crank isn't splined, but there's marks like it so from corrosion getting in the splines that are on the timing gear and balance, you can see in the pic. I can't reinstall the timing gear or harmonic balancer without using a damn sledge hammer. What's the best way to clean this up and get them back on?

 

400 grit sandpaper. Be slow and deliberate.