I'm editing my post. I just tried to do what you are doing in SSIS and I can't figure out a way to merge data without a common key of some sort.
So, the only way I can really think of to get it to work the way you want it to would be to stage the data in separate tables first and then extract the data from your staging tables and use the row number function to create a surrogate key so that you can join both data sets together and insert those columns one next to the other in your destination file.
Another option might be to extract the data from your excel files and use a script task to create a row number column on the fly and then merge join them together based on that row number column which is acting as your common key between the two sources.
You might have to adjust your join to a left outer or right outer if one of your sources has more or less rows than the other.
Kind of a goofy way to get the result you want, but there isn't much use in the data integration world for joining non-related data together.
Maybe someone else has a better option.