Zeroing In on Takeover Targets That Pay : Investments: Those who scour the market with the care of potential acquisitors may come out well ahead.

Wouldn’t it be fun to sell Grumman to Martin Marietta, Paramount to Viacom, Dreyfus Corp. to Mellon Bank?

Mega-mergers are back, and there’s money to be made by investors lucky enough to be holding shares of takeover targets when the suitors come calling.

This is true despite the failure of the proposed merger of Bell Atlantic Corp. and Tele-Communications Inc. In fact, the faltering of that deal may underscore the trend toward slow-to-develop, more cautious mergers.

That bodes well for investors who scour the market with the same careful consideration as potential acquisitors. Even if the sharks never bite, these investors could end up holding some very attractive companies.

And if the sharks do bite, a word to the wise: Don’t hold out for the last dollar.

TCI holders who sold the first day or two after the Bell Atlantic announcement made out very well. Those who held out for the last hurrah are probably regretting it.

Even mergers that are consummated often have a way of losing money for many years after the marriage takes place.

Ferris, Baker Watts economist Robert Brown warns that an increasing number of acquisitions today are being paid for with shares in the parent company instead of cold hard cash.

Wait until the merger takes place, and you can be left with diluted and overextended shares of the adoptive parent instead of the gains of the child.

To find the places corporate shoppers might be looking, consider these points:

* Look for companies that have something to offer in the new and future marketplace. Banks are looking for mutual fund companies and banks with a presence in fast-growing states. Medical companies are looking for managed care expertise, generic drug manufacturers and high-end genetic research efforts already underway. Everyone’s looking for a lift down the information highway.

* Look for companies that have that indescribable something. East Brunswick, N.J., corporate appraiser Russell Parr notes that intangible assets, such as a loyal customer following, good name, history of big image advertising and catalogue of intellectual property such as inventions, trademarks and copyrights, can make a company worth more than its traditional book value or earnings measurement might indicate.

* Look for companies that are selling cheap. In particular, companies that have market capitalization at or below their book value. Even if they don’t get gobbled up, it is the law of the marketplace that undervalued companies rise to their correct values. Remember, in checking this out, that companies might actually be overestimating their book value if they are holding large tracts of land valued at tiptop 1980s prices instead of more realistic post-slump real estate prices.

* Look for companies with cash of their own. Cornell University finance Professor Steve Carvell has long advocated screening for potential takeover targets by focusing on firms that could buy themselves back out of their own cash flow in five or six years. A current price-to-cash-flow per-share ratio of 5 or 6, he notes, means the target is far from hard up for money.

* Look for successful companies. Firms that have high profit margins and strong sales are natural targets. Companies would rather buy companies that are already making money.

* Look for companies that have kept their long-term debts to a minimum.

* Look for companies that have their own little, or large, market niches.