I have a dataset from SDC containing 127 000 M&A bids, including announcement date, year, company name and CUSIP-6. I want to compute CARs (cumulative abnormal returns) using CRSP data, however, CRSP uses CUSIP-8, CUSIP-9, or PERMNO-IDs.

I realize I have to somehow covert my CUSIP-6 to a CUSIP-8 or 9, or create a new unique ID to merge the two datasets. Any tips on how to do this?