The Senate has confirmed veteran test pilot John Krings as the first director of the Pentagon's weapons-evaluation program despite a warning that he has no credentials to oversee combat-type testing. Krings, a former military combat pilot who has worked as a test pilot and head of testing for McDonnell-Douglas for 29 years, was approved 73 to 18 Tuesday for the post of director of the Office of Operational Test and Evaluation.

Sen. David H. Pryor (D-Ark.) said Krings was qualified for any post in the Pentagon except the one for which he was nominated -- the final judge of which weapons will go into America's arsenal.

But Sen. Barry Goldwater (R-Ariz.), chairman of the Senate Armed Services Committee, said that combat-simulated testing goes on daily and that it would be virtually impossible to find someone who has tested weapons in actual combat.

President Reagan, meanwhile, nominated career diplomat Lowell Kilday as ambassador to the Dominican Republic. Kilday, who has been deputy assistant secretary of state for inter-American affairs, would replace Robert Anderson.

Reagan also named Boston University President John Silber to the advisory board of Radio Marti, a radio service broadcast to Cuba.