Was a 400 small block available in 1985 Chevy K1500 4X4?

No, a 400 small-block engine was not available in a 1985 Chevy K1500 4x4. By 1985, Chevrolet had phased out the 400 small block from its light-duty trucks. The most common engines for that year's K1500 4x4 were the 305 cubic inch V8 and the 6.2L diesel V8.