That's one of the things I never liked about excel (the fact that it changes data types). Which is why excel can be bad for creating extracts. Not sure if this will work, but try using the data conversion task for the integers to convert them integers and see if that works.
Another thing I've noticed with excel also is then the excel document already exists it will change anything that is loaded into it into the data type it is using. If the first doesn't work, try creating the output in a brand new location to see if it correctly created the correct data types.
Strick