AUSTIN, Minn. (AP) _ T-shirts celebrating a pink pork loaf in a blue-and-yellow can sold briskly Friday as this town wracked by 13 months of union strife kicked off a four-day celebration of the 50th anniversary of Spam.

Thousands of people were expected to invade the hometown of Geo. A. Hormel & Co. for the Fourth of July weekend celebration.

The local McDonald's was selling Spam McMuffins, and the Jaycees planned a Spam and hotcakes breakfast Saturday.

For $5, visitors to the Chamber of Commerce could buy a blue T-shirt or a blue hat emblazoned with the familiar yellow Spam logo. A Spam piggy bank - a Spam can with a slot in the top - sold for $1, while maple cutting boards bearing the Spam insignia went for $15.

''We have gone through 750 banks in days,'' said Dorothymae Graves of Austin, who was in charge of the ''Spamorabilia'' stand.

Hormel began making the first cans of Spam in Austin in 1937. World War II GIs called it ''a ham that didn't pass its physical,'' and the jokes have never let up.

''There are very few people in the country who have not heard of Spam,'' said Larry Haugen, executive director of the Austin Area Chamber of Commerce.

Residents are hoping some of the festivity surrounding the anniversary will help restore good feelings in Austin, which still is recovering from the meatpackers' strike against Hormel that ended last September. The United Food and Commercial Workers union placed the union local in trusteeship for refusing to end the strike.

After a lull this spring, strike-related vandalism increased in Austin this week. Someone spray-painted the word ''scab'' and obscenities on the home of Mayor John O'Rourke. The home of M.B. Thompson, a former top executive at Hormel, also was spray-painted.

Police Chief Don Hoffman thinks dissident former strikers were responsible, although no arrests have been made.

''I think some of the dissidents are trying to frighten people. They're filled with hate and distrust. They're tearing things apart instead of putting them together,'' Hoffman said Friday.

Barb Collette of the Austin United Support Group, a group composed of former strikers, Hormel retirees and their spouses, said she doesn't know who is involved in the vandalism.

Out-of-work Hormel employees, who have not been recalled since the strike, find the Spam anniversary offensive, Mrs. Collette said.

''I think we're being slapped in the face,'' she said. ''The point is to lead people into believing the Hormel company is beautiful and back to normal.''

The support group plans to enter many of the festival events, although it was denied a permit to sponsor a float in Saturday's parade, she said. A tent city for supporters of the former strikers is being set up outside of town.

''We're having fun,'' Mrs. Collette said. ''No one has had to be told to keep their tempers down.''

All 31 Austin police officers will be on duty this weekend, Hoffman said, adding that he does not expect any disruptions.

''You get that many people and mix in beer, and you'll have trouble. But you'll have trouble in a normal Fourth of July,'' he said.

''I've got a lot of faith in Austin. I think it will be back,'' Ray Waters, 56, a Hormel retiree.