I have a 2458 boxcar that I wish to change to earlier-style box couplers. I am trying to replace a 2954 boxcar, or I would not do this, but wondering how hard it is to get the 2458 apart, as I don't want to break anything. Just the screws on the bottom? This appears to be the only way to get at the rivet-on trucks. I will then purchase earlier trucks and see if I can install. Thx!