Two of the best teams in Division II - No. 1 North Dakota State and No. 3 Central Oklahoma - gained valuable experience competing against a number of top Division II teams last weekend at the Cliff Keen Invitational in Las Vegas.    North Dakota State finished 16th with 52 points and Central Oklahoma was 18th with 47 points.    Central Oklahoma's Muhammed Lawal, ranked No. 1 in Division II, finished second at 197 in Vegas. Lawal lost 3-2 to Lehigh's Jon Trenge, ranked third in Division I, in the final round.    Central Oklahoma's Cole Provine, the defending national champion in Division II, finished eighth at 133.    Two-time national champion Todd Fuller of North Dakota State finished seventh at 174. Fuller won the meet's award for most falls with four.    San Francisco State's Mauricio Wright, ranked second at 184, finished eighth in Vegas.    Fourth-ranked Nebraska-Omaha had three wrestlers place in the top three at the Northern Iowa Open on Sunday in Cedar Falls, Iowa.    UNO's Chad Wallace won the championship at 197. Wallace, ranked second in Division II, defeated Northern Iowa's Sean Stender 7-4 in the championship round. Stender is ranked 12th in Division I.    "Chad was in a tough bracket," UNO Coach Mike Denney said. "That's probably the best tournament he has wrestled for us."    Wallace's teammate, junior Zach Stalder, placed second at 184. Stalder, ranked third in Division II, lost 3-1 to Northern Iowa's Kyle Hanson, ranked eighth in Division I, in the finals. Hanson avenged a double-overtime loss to Stalder two weeks ago.    UNO's Bruce Applegate finished third at 184.