I tried to reate a varchar(70000) on SQL server. It is not possible!
Are your source data VARCHAR or TEXT?
Starting from next release TEXTs from MS-SQL will always be imported a TEXT – also with MySQL 5. However you may need to change to MEDIUMTEXT or LONGTEXT yourself if the length of data demands it.
The MS SQL source was TEXT I believe, because the size was 2147483647, a field used to hold user comments. I can't confirm at the moment because the database is now detached from my development environment and running on the production server.