Quote Frog: "One thing, the coupler on the E7 front end would have to be long enough for the trip pin to clear the pilot."
This would be true of virtually all of the Kaydee-style couplers. There are a few ways around the problem: One would be to cut off the trip pin. Of course, this would leave you unable to uncouple cars automatically, but you may not want to do so anyway.
Another way would be to cut away the bottom of the pilot enough so the couple can swing full width. If you get ahold of some photos of E7's you will not that many of them were operated with the coupler doors closed...especially when on the front end of the train, and the front couple tipped up and back (You'd just leave the front couple off, and cement on coupler doors over the operning. OTOH, some whether on the front end, or as a booster (follower), the coupler doors were left open, and the part of the pilot below the closed doors was rotated back so it is virtually invisible from any sort of distance. You'd need to obtain some coupler doors for an E7, and cement them in the open position on either side of the front of the pilot.
So far as Con-Cor passenger cars are concerned, I operate them with the Kaydee couplers mounted on the trucks. That way they will operate around 18" radius curves without any problems...so long as you are pulling the cars. Backing passenger cars with truck-mounted couplers isn't the most reliable thing. You need to be certain the diaphragms between the ends of the cars do NOT touch, especially on the curves. I prefer to use Walthers' with the paper expansion parts and the smooth plastic endplates, which can be gently bent or curved to prevent them from catching on each other. I cement the endplates to the expansion parts and the expansion part to the end of the car with Walther's Goo. Also, it may be necessary to cut off part of the paper expansion part and to compress what's left with a needlenose pliars before cementing. You will still need to back your passenger trains slowly, and it wouldn't hurt at all to add more weight...at least a couple of ounces to each car. Also, I would go with Con-Cor's 72 ft. or Athearn's 72 ft. cars for best results on 18-inch radius track. Eighty-five foot cars will work on 18-in. radius, but if you run them (say a Great Dome), I'd run a shorter car on each end of the longer ones.