I've a BOX FULL of rolling stock as well but they're ALL 'ole horn style couplers what ta'do? Am sorting out brands, may post a pic when done? Quite ODD: the one Athearn AMTRAK 5221 I have is only one with knuckle couplers (img is from ebay) go figure)! (ps: the trucks are screwed on from the inside how to disassemble chassis? Under those four 'lil buttons on top?) CHEERS!
I converted a few of those to body mounted Kadee couplers last year. The top slides over the chassis and "relaxes" when it gets past the widest part. To remove them, just pull the sides slightly apart in the middle (use a tiny screwdriver if necessary) and the top will slide up.