Acres of red banners and fleets of black limousines have slowly taken over the capital this weekend as Czechoslovakia's leadership, preparing for a Communist Party congress, scrupulously matches the stylized ostentation of its allies in Moscow.

It has been just three weeks since Mikhail Gorbachev consolidated a new era of leadership at the Soviet Union's Communist Party congress. Now, Czechoslovakia is set to become the first of four Soviet Bloc countries to hold similar party meetings meant to set the course of economic and political policy until the end of the century.

Gorbachev's promise of "radical reform" has raised expectations of change around communist-ruled Eastern Europe. Yet, once the 17th congress of the Czechoslovak Communist Party begins here Monday, diplomats believe they will find little to compare with the relatively dramatic events in Moscow.

"The expectations here are moderate, at best," said one western observer of the aging and highly conservative Czechoslovak establishment. "Everyone's feet here are still mired in the concrete of the 1970s. The leadership didn't seem to come back from Moscow with the feeling they should carry out changes."

Czechoslovakia's seeming stasis offers one measure of Gorbachev's still-developing leadership of Eastern Europe. Despite his efforts to rejuvenate an aging command apparatus and introduce economic change at home, the Soviet leader does not yet appear to be pushing similar change on those Eastern European parties that cling to old leaders and orthodox styles.

Instead, the indications are that Moscow's short-term priority for its allies is stability -- however it may be found.

"In order to carry out the kind of changes he wants in the Soviet Union, Gorbachev needs for Eastern Europe to be stable and to provide the Soviets with the economic support they want," a western diplomat said. "Czechoslovakia is one place that can deliver that."

If such expectations prove correct, East European congresses will offer a display of the region's growing diversity during the next three months. For different reasons, Bulgaria and East Germany, with congresses scheduled in April, are judged by western diplomats and East European sources as likely to have activist party meetings and as objects of Soviet concerns.

The other country likely to preserve its status quo, meanwhile, is Poland. There, party leader Wojciech Jaruzelski has pursued radically different policies than the hidebound Czechoslovaks but similarly offered Moscow a prospect of political "normalization." Although threatened by internal hard-liners, Jaruzelski has been so strongly endorsed by the Soviets in recent weeks that Poland's congress in June now appears unlikely to produce either major policy changes or internecine strife.

"We welcome with joy the news that the time of trouble is disappearing," Soviet Foreign Minister Eduard Shevardnadze said in Warsaw this week in the latest Kremlin tribute to the Poles. "Successes have been chalked up -- and all of that thanks to the wisdom, will and energy of the nation and the party with comrade Wojciech Jaruzelski at its head."

The ringing endorsement of Poland's leader has been interpreted by some observers as a sign that Gorbachev eventually will look for more energetic leadership in the Soviet Bloc states. A 63-year-old general of modest personal style who has mixed economic reform policies with political toughness, Jaruzelski may be the East European leader most compatible with Gorbachev, Polish Communist sources say.

In contrast, Gustav Husak of Czechoslovakia, Erich Honecker of East Germany, Janos Kadar of Hungary and Todor Zhivkov of Bulgaria average 73 years of age and have ruled their countries between 14 and 30 years. Zhivkov and Husak, in particular, were closely identified with former Soviet leader Leonid Brezhnev, whose image was discredited by Gorbachev at the recent Soviet congress.

Nevertheless, East European officials remain uncertain about what kind of change, and how much of it, Moscow may eventually seek in the bloc. "It seems clear that Gorbachev doesn't yet have a clear Eastern European policy," said one western diplomat.

The shake-ups in Moscow have been enough to make Husak, the region's most dogged hard-liner, defensive about his position. "Hostile propaganda is spreading slanders that Czechoslovakia is afraid of economic reform," he declared at a regional meeting before the party congress. "We attentively follow the measures being taken in the Soviet Union and the other socialist countries. We are verifying what best suits our conditions and needs."

But in the region's most reformist state, Hungary, Gorbachev's plans for economic change fall well short of reformist experiments there. Hungarian officials are still defending themselves from Soviet suggestions that their ties with the West and capitalist-style measures may be excessive.

"The Soviet Union is in a different stage than Hungary," said a party spokesman in Budapest, who asked not to be named. "The correct thing is that each country look at its specific economic and political conditions and decide on its own best course."

Hungary and Romania, the only two Warsaw Pact countries that will not have their party congresses this year, are unlikely to shift policies as a result of the Soviet congress.

The shake-ups of the Soviet congress have been paralleled most closely in Bulgaria, and the impetus appears to have come from Gorbachev, who during a visit to Sofia last October showed displeasure with Zhivkov. Since then, Zhivkov has announced economic changes, shifts of high-level personnel and anticorruption steps evidently designed to jolt Bulgaria out of a serious economic slump as well as to mollify Moscow. Diplomats now expect further changes at Bulgaria's party congress and do not exclude the possibility that Zhivkov soon may be forced from power.

While Soviet strategists clearly are concerned about economic and political stagnation in Sofia, East Germany's Honecker presents a different potential challenge. Western diplomats believe Honecker's stubborn pursuit of improved ties with West Germany has tempered Soviet enthusiasm over East Berlin's success in creating the fastest growing and most technically advanced economy in the communist world.