It will be tough for General Motors Corp. to increase its share of the midsize sport/utility vehicle (SUV) market with its all-new Olds Bravada, GMC Envoy and Chevrolet TrailBlazer models, admits Richard Spina, assistant vehicle line executive-midsize trucks. GM lost 18,000 units of production in a recall and subsequent shutdown of the Moraine, OH, plant earlier this year. Moraine has raised output to 1,200 trucks per day from 1,100 daily. Of that, up to 50% of production is dedicated to TrailBlazer, 40% to Envoy and 10% to Bravada. Mr. Spina expects sales to exceed last year's 350,000 units. GM is using incentives of $2,000 on the new SUVs and $2,500 on the old Blazer, but Mr. Spina says GM's incentives haven't matched Ford's. With its three rows of seats, Explorer has an advantage — GM won't begin producing a new 7-seat model at its Oklahoma City, OK, plant until 2002. Preproduction begins in the fourth quarter of this year, and the 7-seater is expected to eventually account for 45% of volume.