At 10:53 AM 3/16/2012 -0700, you wrote:

As Tony says, IM's Santa Fe Caswell gondolas are nice models and, as
there were more than 10,000 of them, did go off-line fairly
frequently

I thought I had one of these but I can't find it. But undec kits are in stock at IM. I also have some of the USRA composites but they lack the appeal of the others - their profile is too similar to an ordinary gondola. I also see IM has announced 8 different variants of the Caswell in RTR form...

Sunshine has also produced resin kits for the later Santa Fe 40' and 50'
composite gons.

I also have at least one of these maybe both. There was a time when I bought one of everything, before I decided to focus more on the 70s. I am still interested in steam era freight cars, but not to build a massive fleet. I still have mumble-mumble steam locomotives, and quite a few of them are western prototypes.

UP's GS gons can be modeled, with some modifications, using the old
Ulrich die cast metal kits for the G-50-7 class

The Ulrich is what started it for me. My dad had a modest selection of metal freight cars from Athearn, MDC, and Ulrich. The Ulrich gondola was impressive to me at the time with its crisp detail and working hatches - although it was done up in a very loud, and I'm sure bogus green M&STL scheme.
http://www.gp30.com/vintage/dadstrain/dadstrain06.jpg - I haven't tried to bring one up to semi-current standards but I have accumulated some unbuilt kits cheaply over the past several years.

41'6". A few eastern and midwestern RRs (e.g. B&M, C&EI, Monon) had
GS gons, but they weren't Enterprise cars and in most cases were
converted in the '30s and '40s to solid bottom cars.

The Monon car sounds vaguely familiar.

So modeling GS gondolas other than the Enterprise cars is still a
largely unexplored frontier.

I feel I'm ready to take a crack at some fairly major scratch-bashing, but good data is a must. I like to take a break now and then from my main interests and it would be fun just to model some of the SP variants to start with. I first need to take inventory of what I have. I know I have two DA kits, but I never even realized there were more than one variant so I don't even know what I have there.

Andy