Recent promising theoretical results for irregular repeat-accumulate (IRA) codes, together with their extremely simple encoding, motivates this investigation into the design and implementation of finite-length IRA codes. In this paper interleavers for RA codes are designed using combinatorial techniques to produce RA codes with Tanner graphs suitable for sum-product decoding. Further, a modified RA code accumulator is used to construct new IRA codes with columns of weight 3 in the accumulator. These new codes, called w3IRA codes, can be designed with flexible degree distributions and retain the simple encoding of traditional IRA codes.