Arkansas Republicans selected their final seven delegates to the GOP National Convention today, endorsing four as uncommitted and one each pledged to Ronald Reagan, George Bush and John B. Connally.

The biggest surprise was the failure of Senate Minority Leader Howard H. Baker Jr. of Tennessee, who won four of the 12 delegates selected in district caucuses two weeks ago, to get any of his supporters elected this time. One Baker worker said that on the eve of the vote, it had been anticipated that the Tennessee senator would get three delegates.

Thus Reagan, the former California governor who won the Arkansas presidential primary in 1976 and picked up six supporters in the district caucuses, officially holds the lead with seven of the state's 19 delegates. Bush, the former CIA director and U.N. ambassador, has two delegates; former Texas governor Connally has one, and five delegates officially are uncommitted.

Baker made a last-ditch attempt Friday night to woo Arkansas delegates with a quick appearance at a Little Rock reception. Although he officially won no delegates today, Baker is known to be leading for the support of two of the uncommitted delegates.

Two of the delegate seats were filled within eight minutes today by the 210 certified members of the Republican State Committee. The first went to Rep. John Paul Hammerschmidt, who in 1966 with the support of Winthrop Rockefeller became the first Republican to be elected to Congress from Arkansas in 94 years. The second went to freshman Rep. Ed Bethune, the first Republican elected in the second district of Arkansas in 96 years.

Elected after nearly another three hours were: State Party Chairman Lynn Lowe of Texarkana; National Committeewoman Leona Troxell of Rose Bud; Ada Mills of Clarksville, co-chairman of the Connally campaign in Arkansas; Horace (Pete) Sickel of De Valls Bluff, campaign chairman for Reagan in the second district, and Eijah Coleman of Pine Bluff, the only black delegate, who was nominated for three of the seven positions, and finally won the last delegate seat available.

Hammerschmidt, the most vocal supporter of Bush in the state for months, added to the surprises today when he nomimated Mills, a long-time party worker and Connally supporter against a candidate publicly pledged to Bush.

The congressman said Mills asked him to nominate her Friday night. "I think that vote will eventually come to us," he said. "I don't want to be presumptuous on that but I think it will if Connally is not in the race."