The San Francisco 49ers today answered for themselves one of the last lingering questions about how good they are.

The 49ers came into Three Rivers Stadium and intimidated the usually intimidating Pittsburgh Steelers. In the process, they earned a 17-14 victory and increased their winning streak to six games, the longest in the National Football League.

"The one thing we hadn't done this year was play a tough, physical team on the road and come from behind and beat them," said 49er quarterback Joe Montana. "Today we beat probably the most physical team there is and we did it in a place where they don't lose many games to anybody. We proved a lot to ourselves."

In improving their record to 7-2, the 49ers became the first NFC team to win here since 1971, and except for three bad plays in the third period, they made it look easy. San Francisco remains two games ahead in the NFC West.

The 49ers forced six Pittsburgh turnovers (three interceptions and three fumbles) and so intimidated the Steeler wide receivers that after the first period, Terry Bradshaw didn't complete one pass deep over the middle. Jim Smith and John Stallworth had to leave for a short time after taking hard hits on patterns over the middle.

"We said all week that the key to the game was to hit with Pittsburgh," said San Francisco Coach Bill Walsh. "We went after them physically and held our own."

Play was rough throughout the game, with shoving continuing between plays. The officials called three offsetting personal foul penalties to try to maintain order.

San Francisco, trailing, 14-10, started its drive to the winning touchdown midway through the fourth quarter, when Carlton Williamson, a rookie from Pittsburgh, intercepted a badly overthrown pass Bradshaw had intended for Bennie Cunningham. Williamson returned it 28 yards to the Pittsburgh 43.

A 23-yard gain on a Montana-to-Freddie Solomon pass and a holding penalty on Mel Blount helped the 49ers get to the 13.

Walt Easley, a 49er rookie from West Virginia who was playing only because Johnny Davis had a pulled calf muscle, took over from there. He ran over his left tackle for three yards, passed five yards to tight end Charlie Young on a halfback pass, ran over his right tackle for four yards to the one and then ran around his left end for the last yard and the winning touchdown with 5:35 to play.

The 49ers had taken a 10-0 halftime lead before the Steelers converted two interceptions into touchdowns. Montana, trying to throw the ball away, didn't get enough on it and cornerback Blount intercepted on the right sideline and ran 50 yards for a touchdown.

David Trout's extra point cut the 49er lead to 10-7 and on San Francisco's next possession, again while the 49ers were moving well, Montana misread a pass coverage and was intercepted by Jack Lambert.

Lambert returned 31 yards to the 22 and on first down, Bradshaw threw a touchdown pass to Smith, who beat Ronnie Lott and Williamson to the outside. Trout's conversion put the Steelers on top with 6:39 left in the third quarter.

That touchdown pass was the Steelers' only play from scrimmage in the third period until they got the ball back with l:30 left after Tom Beasley blocked a Ray Wersching field goal attempt.

After the 49ers had regained the lead, the Steelers moved to the 49er 34 before running out of downs with 67 seconds remaining.

The Steelers had a third and one at the 34, but lost two yards on a pass from Bradshaw to Randy Grossman. Under a heavy pass rush on fourth down, Bradshaw threw wildly and the pass fell incomplete.

"We were confused on that third-down play," said Pittsburgh Coach Chuck Noll. "We wanted to run one of two plays depending on what defense they were in. We took too long in the huddle and then at the line of scrimmage there wasn't enough time to audible and the play just didn't work."

"I wasn't surprised that San Francisco played so well, but I was surprised that we played so poorly," said Bradshaw, whose 125 passing yards were his fewest of the season.

The 49ers scored their 10 first-half points in the final 37 seconds of the second period.

Montana moved them 46 yards in eight plays after Eric Wright intercepted Bradshaw. The touchdown came on a five-yard pass from Montana to Young.

On the first play after the ensuing kickoff, Pittsburgh's Frank Pollard fumbled to Williamson. Three plays later, with eight seconds left in the half, Wersching kicked a 45-yard field goal, his longest of the season.

Montana completed 22 of 37 for 205 yards. "We control the ball with short passes instead of with the run," said Walsh.

Montana, who went into the game as the NFC's leading passer, had his string of 122 passes without an interception broken by Blount.