A 6-foot-3 real estate developer with a long record in local politics, New Jersey Assembly Minority Leader Dean A. Gallo took advantage of a fortuitous court decision on redistricting to topple Rep. Joseph G. Minish (D).

In 1982, Minish won his 11th term with 64.3 percent of the vote, but in February, a three-judge federal panel shoved him into an area so far from his old base in the Essex County towns near Newark that Gallo knew he had a plum to pick.

Gallo, 48, was born in Hackensack. With a few courses but no degree from the University of Southern Florida, he has spent his life, like his father before him, in the local real estate business, while steadily climbing the ladder of local elective office.

He won a seat on the Parsippany-Troy Hills township council in the late 1960s, moved up to the Morris County Board of Freeholders and then to the state Assembly in 1975. He compiled a moderate record, holding out strongly for business interests but also compromising with the Democrats in control of the legislature.

Gallo received strong support in the Republican areas of Morris County, whose addition to the district poisoned Minish's reelection chances.

Gallo said he intended to push hard for a balanced budget, supporting President Reagan's call for a constitutional amendment and line-item veto authority. He also wants a quick reauthorization and funding increase for the federal "Superfund" to clean up toxic-waste dumps in his area.

Gallo and his wife, Anne, a retired schoolteacher, have two children, Susan, 27, and Robert, 25.