The speedometer cable I used in my LJ78 is 83710-90K06, the part number cross reference at Toyodiy shows several models of HZJ77, but not the -PEU. Not sure what the difference there would be. ToyoDIY.com - https://www.toyodiy.com/parts/xref?s=8371090K06&mJ=on
@coldtaco just posted about building a seat, not sure if the foam pads he used are the same as in your 77 though. Builds - AK HJ-75 - https://forum.ih8mud.com/threads/ak-hj-75.930702/post-14732079