Tom,
I can't judge on the skill of the person who's cars you saw. AM used to have (maybe still does) a separate sale mounting pad for their Budd cars, but I've got no experience with them. I just use the standard AM talgo Snap-Lok on my Budd's. The distance seems fine that way.
For the older AM 85' smooth side cars and the heavyweights, I had to build up pads and use my judgment on those, in fact I might have my smooth sided cars a little too close.
As far as the freight cars go, As the SHS cars were already predrilled for 802's I used their mounting holes.
For AM, most of the time I just ran a 00-80 screw through the existing 2-56 hole and secured it with a nut on the inside, then drilled a small hole in the underframe so I could stick a piece of plastic rod through the 802 box's rear mounting hole so the coupler box wouldn't rotate. Simple, but effective.
For PRS, I didn't use their coupler box, I mounted the 802's, using the PRS mounting hole as a locating guide. Then three screws through the box's mounting holes.
The DesPlaines HiRail coupler box has the same "footprint" as an 802, so it's a one for one exchange. I'll also reuse the DesPlaines' centering spring, it's stiffer than Kadee's.
Rusty
