Data merge- Address matching

The project is to merge datasets. I have a master dataset of 50,000+ entities. This data includes business name, business address, longitude/latitude, etc. This is in text (tab delimited) format. Then, I have a file of about 10000 entries each that contain business name, address, longitude/latitude. The names and addresses will match but not always textually exactly. (For example, the address in one might say 5158 S Windsor Dr and the address in the other might say 5158 South Windsor Dr). Please specify how you would do this. By hand is one possibility, but you must have facility with US address/language conventions.