Thanks all for the info on 7311. Certainly a unique unit.

I used to know a lot about interchangeability (or lack thereof) among the various switcher truck designs and manufacturers, but most of that's been relegated to my memory's scrap heap, now that I don't work on that stuff anymore.

... do recall there are (at least?) 2 versions of the Flexicoil 2-axle... for instance, EMD FL-9's use a longer version as the lead truck.

... also recall that the Alco "tri-mount" truck has a radically different "bolster" arrangement than most early EMD stuff... would be curious to know how they adapted those trucks to the 7311's frame... and, since EMD apparently built it to accept those trucks, exactly what you'd have to do to convert it to Flexicoils. If possible?