"Hi: no. The only datum I could find was from the 1943 CBC safety appliances as follows ( a paraphrase ) the ends of the running board shall be no less than 6 or more than 10 inches from a Vertical plane parallel to the end of the car passing thru the inside edge of the closed knuckle with coupler horn against the buffer block or end sill. How you can translate this to model overhang I don't know. Marty cooper"

Easy. The knuckle to coupler horn dimension has been a consistent 12" since the Type D coupler was adopted around WWI; older coupler designs were smaller, more like 9", but few on this list model equipment from that earlier era. This means the running board should project between 2" to 6" beyond the striker, which is the end of the center sill, or "coupler box" in model parlance. Length over the strikers is one of the basic dimensions given on prototype car drawings, if not directly, then found by adding the truck centers plus 2X the kingpin to striker distance. Also the "outside Length" dimension given in the ORER is the length over the strikers in most cases.

Dennis Storzek