ARE WE going to get the best tax bill that money can buy? You could get that impression from the reports of PAC contributions filed with the Federal Election Commission by members of the House Ways and Means and Senate Finance committees. According to FEC figures as compiled by Common Cause, these 56 legislators received PAC contributions totaling $3.7 million in the six months ended June 30. In the corresponding period in 1983, the same members received $1.2 million.

Now, we understand that campaign contributions are not bribes, and we know that many PACs aggregate the small contributions of a lot of little people who might not give on their own. We maintain, nevertheless, that this is a seamy situation. For the fact is that these PAC members, and many people who make individual contributions, are not disinterested or acting out of abstract motives. They're trying to further their own financial interests. They have every right to enter the political arena. But their massed contributions tend to distort the workings of the system and give undue weight to interests that are well-organized and well-heeled.

For this the congressmen may be more to blame than the contributors. The tax-writing committee members are not just passive recipients, beneficiaries of an unpredicted bounty. They are going out and seeking the money. Lobbyists are groaning at the number and cost of the fund-raisers for which they feel compelled to buy tickets. The politicians evidently see their work on the tax-reform bill as an opportunity to fatten their treasuries and deter serious opponents. Earlier this year, when Sen. Russell Long announced his retirement, the politicians saw Ways and Means member Henson Moore (R-La.) become the odds-on favorite for the 1986 Senate race, because Mr. Moore had some $750,000 in the bank. He has raised $695,000 more this year. It doesn't hurt to be on Ways and Means.

Four years ago, when Ways and Means Democrats tried to outbid Reagan Republicans in tax breaks, David Stockman said the hogs -- the lobbyists -- were really feeding. This year the most ravenous appetites seem to be on the congressional side of the trough. The most lavish givers -- they include real estate, insurance, oil and gas and banking interests, as well as labor PACs -- are trying, as always, to create a climate that will sway decisions and undecided votes. There's a danger, as always, that they will succeed. It will be worth watching the tax-writing committee votes closely to see what the big contributors get for their money.