What a great series of replies! Thank you! But now I'm getting nervous!
I need to stress: I will NOT be buying Marx, Ives, or any older stuff. I understand the comment made above about older trains being designed to run on smaller curves given the times.
I don't know if it matters, but ALL of my switches are O27 profile K-Line low-profile (newer style) switches. I no longer own any Lionel switches because the motor housing issue was one I couldn't live with.
I was at the local hobby store Wednesday and the owner was kind enough to allow me to try an engine and tender combo (new one since it had the newer MTH drawbar) on 27" curves and 1 switch that I took there. I didn't actually run the train, I slightly lifted it to take the weight off so as to not damage the traction tire, and manually moved it around the track and thru the switch. It handled it.
But after reading above about the flange issue now I'm wondering if the flanges would have been an issue had I not slightly, and I mean slightly, lifted the drive wheels off the track. But the tender handled it and I didn't lift that.
Boy, this is confusing.
Jim, I like your suggestion about coming back once I have a model in mind and possibly someone here will own that model and be willing to try. I plan on buying 2 trains at this October York so I probably won't know until then unfortunately.
Alan, I would still appreciate it if you could try. I agreed to commit today to the fellow buying my stuff but I'll ask for a weekend reprieve. I'm sure he'll understand.
thanks - walt