A balancing problem for transfer lines with workstations in series and simultaneously executed blocks of operations is considered. Inclusion constraints related to operations and exclusion constraints with regard to blocks as well as precedence constraints are given. The problem is to choose blocks from a given set and to assign them to workstations while minimizing the line cost and satisfying the above constraints. A combined heuristic approach is proposed. It is based on decomposition of the initial problem into several sub-problems and solving them by an exact algorithm. Results of computational experiments are presented.