Rebuilding C 648

I own two Pan Handle Rusty Route cabooses and one is in far better shape than the other. I'm starting with the most distressed and in need of repair, number 648. Built from a Silver Streak kit with full interior and lighting, the car is a fine example of what could be done by a skilled modeler in the 1960s to create a car with detail and charm. Sadly it has seen better days, but happily the repairs needed are straightforward.While I'd like to light this car again in order to showcase the interior work, that's not a project I want to tackle at the moment. My goal for now is to rebuild the car to running condition, mechanically sound first, address a "weighty" issue, and get it back on the rails behind #225 within the next month. I'll leave the roof removable for now in order to add lights eventually.The chief mechanical defect is a frozen coupler. I had originally planned to replace it with a nearly identical one from my parts bin but decided I had nothing to lose by trying to unstick…