With this paper we aim to show that Gaussian sums particle filtering (GSPF) combined with iterative frequency-domain equalization (IFDE) for single-carrier (SC) modulations offer an appropriate solution for data transmission over highly frequency-selective channels with strong phase noise and linear drift. We present a promising IFDE scheme dubbed iterativeblock decision feedback equalization (IB-DFE) and propose a post-equalization phase noise estimation scheme within the iteration chain. In fact, by exploiting the Gaussianity of the equalizer output we are able to track the phase noise value by updating the state posterior distribution using the GSPF algorithm. Additionally, simulation results are presented considering QPSK, 16-QAM, and 64-QAM signalling in highly frequency-selective channels and different values for the phase noise variance and linear drift.