Yes, as has been explored there are very few options with the JET driver (don't know about the ACE driver). The number of rows read to determine the data type can be changed, or else you need to have the alpha character in the first few rows for string columns.

If you have a header row you can include it as data rather than a header and set all rows as text in this way, in the data flow you ignore the first row then manually convert any numbers to the appropriate type.

Or else if you can have 2 header rows, the first being your regular header row and the second being a datatype setting row, then you can set the first row as headers as normal, and the second row will be included in the data to set the data types but you filter it out later.