Speaking of the $1 trillion national debt (as we often do), officials of the National Tax-Limitation Committee said yesterday that the deficit projected in Reagan's budget has been of great help in their efforts to get a constitutional amendment passed that would make a balanced budget virtually mandatory and would prohibit the rate of federal tax growth from exceeding the rate of growth in national income.

Lewis K. Uhler, president of the group, claimed he is close to the 67 votes he needs to pass the amendment in the Senate, where a vote is possible this spring. The House, he conceded, will be a tougher hurdle. Uhler's group is also pushing the campaign in state legislatures; 32 of the necessary 34 have called for a constitutional convention to consider the amendment. Uhler once headed a task force that studied tax reduction for Gov. Ronald Reagan in California. President Reagan has historically expressed support for such an amendment, but others in the White House (like many in the House) are concerned that it would make financial management of the country rather dicey, given the present state of the nation's finances. The earliest the amendment would take effect, Uhler said, would be fiscal 1986.