NAT'L COMPUTER <NLCS.O> TO BUY DATA CARD STAKE National Computer Systems Inc said it agreed to acquire Deluxe Check Printers Inc's <DLX> 38 pct stake in Data Card Corp. National Computer said it plans to issue 45 mln dlrs in five year subordinated convertible debentures to purchase the 3,749,401 shares of Data Card from Deluxe. Completion of the proposed transaction, subject to regulatory approval, is expected in mid-July, it said. The debenture will bear an increasing rate of interest over its term, with a 7.3 pct weighted average rate and will be convertible into National Computer common stock at 20 dlrs a share, it said. Separately, Deluxe said its Data Card investment no longer fits its business strategy. Deluxe has held an interest in Data Card since 1975 when it provided funds for Data Card to buy Troy Computer Products Corp. In November 1986, Data Card said it planned to sell its Troy division.