What to Consider if You Want to Join in Now : Investing: Though many pros say rallies haven’t run their courses, they warn against going overboard.

Is there still time to make money in the markets betting on a weaker economy? Probably, many Wall Streeters say. But most warn not to get carried away.

The bond market has been rallying for two months, anticipating the slowdown that seemed to be hinted in last Friday’s January employment report.

Likewise, the stocks that benefit most in a slower economy--stable-growth issues such as household products makers--have already zoomed.

Even so, many pros say the rallies haven’t fully run their courses. Some strategies if you believe in a slowdown:

* Bonds. The drop in longer-term bond yields since November has already produced hefty capital gains for investors who bought bonds at their peak yields.

The price of the 30-year U.S. Treasury bond, for example, has appreciated 7.5% since mid-November, as the bond’s yield has fallen from 8.16% to 7.62%.

Other types of bonds have rallied as well. The Vanguard California Insured Long-Term Municipal bond fund has gained 4.9% since Jan. 1, nearly making up for the fund’s 5.7% negative total return for all of 1994.

With inflation subdued and the economy easing, long-term bond values should continue to appreciate gradually as market yields move lower, argues John R. Williams, economist at Bankers Trust. He sees the 30-year T-bond yield ending 1995 around 7%.

But any additional decline in yields won’t be straight down. Indeed, Wall Street fears that even if new data supports the idea of a slowing economy, pent-up price increases this winter and spring could produce minor inflation flare-ups that would temporarily spook bond owners. A big test comes this Friday, when the government will report on January wholesale inflation.

Kevin SigRist, economist at Norwest Corp. in Minneapolis, advises clients to buy intermediate-term Treasury notes (those maturing in two to 10 years) and mortgage-backed bonds on what he expects will be periodic selloffs.

The bond bulls look at it this way: Even if they’re wrong, and yields haven’t yet peaked in this economic expansion, current yields still are well above year-ago levels and well above inflation. With 2-year Treasury notes now paying 7.13%, that’s a decent return to be stuck with even if market rates surge again, the bulls say.

Federated Investors economist Henry Gailliot, who believes the bond market is just enjoying a rally in a bear market, figures that the future peak in yields that he foresees may put the 30-year T-bond over 8.25%. Someone buying that bond now, at 7.62%, would take a loss if that happens--but it wouldn’t be on the scale of last year’s losses, when bond yields rose 2.5 to 3 percentage points.

* Stocks. Friday’s big rally on Wall Street was led by stocks of financial services companies, including banks, brokers and insurance companies. They would benefit from any sustained decline in interest rates because their cost of financing would decline.

Those stocks also have something else going for them, said James Engle, chief investment officer at Wood, Struthers & Winthrop in New York: They sell for cheap prices relative to earnings per share.

“We still think the financial companies are very attractive here,” said Engle, whose favorites include Federal National Mortgage Assn. and Wells Fargo.

Classic big-name growth stocks like Walt Disney and Pepsico, meanwhile, could continue to attract buyers if Wall Street increasingly sours on industrial stocks whose fortunes are tied to the economy’s swings.

But a bigger beneficiary group may be smaller growth stocks, many of which have been hammered over the past year as interest rates rose. Higher rates automatically reduce the prices investors are willing to pay for riskier small stocks, relative to their earnings.

If long-term interest rates continue to decline, however, the reverse should be true: “Falling rates should be good for (smaller) stocks, because it will improve the (price-to-earnings) multiple” that the typical investor is willing to pay, said Ron Ognar, manager of the Strong Growth fund in Milwaukee.

Finally, some Wall Streeters believe a continuing bond rally that stems from more moderate economic growth will be good for many different stocks. Rao Chalasani, strategist at Kemper Securities in Chicago, advocates a balanced portfolio of consumer, financial and industrial stocks.

“A slowing economy is bad for stocks only if it’s associated with being forced” by a Fed intent on bringing on recession, Chalasani said. “What this Fed wants is just some moderation.”