I appreciate all the input. Since I wanted to keep this as "stock" as possible, I went the route of mounting to the original coupler "arm".
I did find a stash of Weaver #700 couplers; although these are plastic, I've used these on some rolling stock (and the KD #806s on my F units) without any problems, so I'm not as "anti-plastic" as some of you.
In any case, I drilled a 700 and mounted it and here we are now:
And here is the photo I posted earlier of the Athearn coupler:
Although the lighting is different, I hope you can see the improvement.
When I get some metal KDs, I will give one of those a shot as well. I get what you're saying about "metal vs. plastic"; I really do.
Just making do with what I have on hand...
Mark in Oregon