The two men who run Congress - a former Boston grocery boy and the adopted son of a West Virginia coal miner - yesterday had some good news - and some bad - for federal union leaders.

If you work for Uncle Sam, get or send mail, pay taxes or care about the American political process, the predictions apply to you, too.

Good news for the union leaders is that a postal "reform" bill dear to the AFL-CIO's heart will probably be cleared by the House before the Easter recess.That forecast comes from Speaker of the House Thomas P. (Tip) O'Neill Jr. (D-Mass.). His insights and clout qualify him to speak with authority on such matters.

The bad news for AFL-CIO employe leaders who are here for an education and lobbying session concerns Hatch Act changes. The House-passed bill that would allow the 2.7 million government workers to get into politics faces talkathon in the Senate. That assessment was made by Majority Leader Robert C. Byrd. He doesn't make many mistakes when he takes the pulse of the Senate.

Byrd told several hundred delegates to the AFL-CIO's Public Employes Department session at the Shoreham that he expects a filibuster attempt to block any liberalization of the Hatch Act. That 39-year-old law has kept 2.6 million federal and postal employees out of partisan politics as candidates, campaign managers or money-collectors.

The House has passed the Hatch Act liberalization. The White House has blessed it as opening the door to full, democratic political participation for the nation's best-paid, best-trained and most important bloc of voters - the people who run the daily operations of the U.S. government.

Opponents of Hatch Act changes argue that the democratic political participation would be with a capital "D" and make it easier for political bosses to squeeze, staple and mutilate bureaucrats once they are freed from the no-politics law.

O'Neil told a breakfast session of the Public Employe Department leaders - whose unions represent more than half the federal work force - that the postal reform bill they want will be out of the House before members leave town for Easter vacations next Friday.

AFL-CIO unions represent 9 of every 10 of the postal service's 600,000 rank-and-file workers. The unions say the "reform" measure is necessary to save the U.S. Postal Service from pricing itself out of business, and putting many postal workers and private mailers out of work.

The bill would replace the present business-oriented management of the USPS with a presidentially appointed postmaster general and increase subsidies to the USPS. It has undergone several rate increases (and, wants another) since going to a semi-pay-as-you-go system.

It also would give AFL-CIO unions more power to represent workers, cutting out independents who have not been able to win bargaining rights.

Byrd said 60 votes would be needed to shut off a filibuster against the Hatch Act. Even if they can be mustered, Byrd warned the ability of some senators to block consideration of legislation "has been honed to a very fine edge."

Byrd said the long-running coal miners strike is "not helping" senators who want to push through labor reforms, including Hatch Act changes.

Non-federal union leaders at the conference are anxious to see approval of Hatch Act changes affecting federal and postal employes so they can push harder for repeal of various "little Hatch Act" restrictions covering some of the 12 million state and local government workers.

Veterans Preference: Sen. Alan Cranston (D-Calif.) says there is "no chance" Congress will approve the White House plan to eliminate the preference that military veterans get in federal employment. One of the "reforms" in the Carter shake-up of the civil service would eliminate the lifetime break veterans now get by law when applying for federal jobs, and special retention benefits they have during layoffs.

Cranston is assistant majority leader of the Senate and a ranking member of the Veterans Affairs Committee that will consider the Carter plan. Most of the nation's veterans groups - who have a powerful lobby on Capitol Hill - oppose any change in veterans preference laws, which the White House say have discriminated against women and blacks in federal employment.