Obviously many of the veficles use comman compnents, the current russian tank engines for example. However, the "pieces" stored made or purchased are specific to each model - why? Additionally Tigers and Panthers used the Maybach HL 210 the HL 230 engines but their models appear (superficially) very different. Obviously the american tanks use some common components although the choice of model (A4E8) and vehicle (GMC M10 and forthcoming M18) allow specific differnces to be shown on what are a family of related vehicles.