We consider in this paper the concatenation of a high rate punctured convolutional code and a precoded intersymbol interference (ISI) channel separated by an interleaver. The goal in this work is to develop design techniques for the interleaver and precoder for a given ISI channel where the design criterion is to obtain the lowest error rate floor. Our results show that an S-random interleaver is an appropriate choice for this system and that the optimal precoder may be selected through the use of what we call truncated conditional distance enumerators. Simulation results support the techniques developed.