PCRR/Dave
Where did I say I modified my rolling stock to run on 0-31 track. ALL Lionel 'O' gauge tinplate ran on 0-31, and MHT reproductions are exact copies of the Lionel originals, except for the couplers on the small cars (they fit too tight).
Walt
That lift pin is making the coupling too tight.
For proof of good 0-31 tinplate running go to YouTube:
O Tinplate Carpet Layout (it's a Capital O not a zero)