The U.S. House of Representatives signed off on a $1.1 trillion health-care overhaul this weekend that would transform the way the industry conducts its business. But the bill faces heavier opposition in the more moderate Senate, leaving a giant question mark hanging over the entire reform effort.

Not exactly the time to be jumping headfirst into health-care stocks right? Wrong, says Ed Yardeni, president of Yardeni Research and a former chief investment strategist at Deutsche Bank.

Pointing to the sector’s current valuations and its performance during the attempted overhaul in the early 1990s, Yardeni said now is precisely the moment to scoop up health-care stocks, especially big pharmaceutical stocks that have higher dividends.

In a note to clients, Yardeni said the S&P 500 health-care sector’s relative price to earnings ratio fell to a then-record low of 0.84 when President Bill Clinton introduced his reform plan in April 1993.

The sector’s P/E climbed to 0.98 as the plan was gradually watered down and then jumped to 1.08 as passage appeared to be doomed in August 1994. By the spring of 1995, health-care stocks were back in the 1.2-1.4 P/E ratio, Yardeni said. From its low in 1993, the S&P 500 health-care sector outperformed the broader S&P 500 by more than two times over the next two years.

“It could be déjà vu with PelosiCare in 2009. The sector is currently trading at a discount to the market again,” Yardeni said, pointing to a new record low P/E ratio of 0.76 reached in April, and not far from where the current ratio sits.

“There probably is a reform rally here somewhere,” said Dave Shove, an analyst at BMO Capital Markets. ““It’s fairly easy to make an argument that whatever happens from here on out is not going to move the fundamental trajectory a lot.”

Health-care stocks like Aetna (AET) and UnitedHealth (UNH) rallied modestly on Monday in the wake of the House vote as the narrow passage in the lower chamber underscores the tough road ahead in the Senate.

“We think there is plenty of room for the relative P/E to rise whether PelosiCare happens or not. The second option would obviously be more bullish for the sector,” Yardeni said.

This weekend’s close vote “means we are no where closer to getting that done,” said Art Hogan, chief market strategist at Jefferies & Co. “The longer it takes, the less likely it will happen or less arduous it will be on health-care profits.”

Health-care overhaul or not, the managed-care and pharmacy benefit management industries still face a number of issues in the wake of the recession, including growing medical costs, weak investment income and a lack of new members due to high unemployment.

“The fundamentals there aren’t great,” said Shove.

Faced with those headwinds, a number of these health-care companies have cut their 2010 earnings estimates, which are now mostly flat from 2009, said Shove. “That to me does not argue for a tremendously bullish scenario to say, ‘Rush in and buy,’” he said.

Even if the health-care overhaul is signed into law before the end of the year, the sector could benefit as the huge cloud of uncertainty would mostly be lifted.

“Generally speaking when uncertainty goes away, things get a little better,” said Shove. “There are an awful lot of investors who want to know the answer before they are going to make this choice. And that’s certainly not a stupid way to approach this.”