I have been resisting responding to the initial question about modeling the FGE/WFE/BRE steel cars simply because the answer is not simple, but I will try to keep it short and provide some possibilities.
First there is only one group of kits for any of the FGE/WFE/BRE steel cars and these are offered by Sunshine. These are the cars built in the early 1950's with sliding doors. These will build into accurate models with one exception. The consortium used an odd version of the Improved Dreadnaught end where the top large corrugation is straight along its bottom, creating an asymmetrical rib. The BRE cars featured two different versions of the ID end where there are small differences in the lower portion of the stamping. All of the FGE cars carried FHIX reporting marks while some of the WFE cars carried WFEX reporting marks and some were WHIX. The "HI" signaled that these were "Heavy Insulation" cars with six inches in the sides instead of the more typical 3½ inches.
I have 3 or 4 undecorated Accurail plug door cars which I want to use to model Fruit Growers RBNX 80000 series examples. These were insulated "RB" type cars. These will require de-laddering and other similar detail removal.
I have not studied the InterMountain kits closely yet to see what potential they present to build consortium reefers built in 1947 and after. The PFE 40-10 possibly can be used to model the fifty WFEX 67895-67999 pre-war cars with the only surgery required "I think" being replacing the door hinges with Grandt Line parts. BRE had 270 prewar cars, BREX 74730-74999 that were similar to the WFE cars except for the ends, which featured a very odd bifurcated rib stamping.
By creating a straight continuous side sill, the IM PFE 40-23 possibly can be used to model BRE's only postwar hinged doors cars (74200-74399) by replacing the hinges and setting the door locking lever at what appears to be a 45 degree angle rather than 90 degrees. Again there is the issue of the ID end with that pesky asymmetrical top rib but I can live with this. The same kit can potentially also be used to model the WFE's 68400-68649, but here the PFE style hinges are correct for this group. This kit could perhaps also be used to model FGE lone aluminum car, #40000, by changing the hinges and substituting a rectangular paneled roof. These had the ID end with the more typical symmetrical top rib, but rode on Roller Bearing Andrews trucks!
FGE 39300-39499 and 39500-39799 series can potentially be modeled by creating a solid continuous side sill and replacing the door hinges. Having said all of this, I have not studied the 40-10 and 40-23 models to see how the rivet patterns match up, nor have I looked at how the brake arrangements will compare but any changes to the brake systems would be easy. I have not done any dimensional comparisons either.
The other hinged door cars built by FGE and WFE in 1948 and 1949 featured welded sides, seven panels on each side of the door. FGEX 38635-38999 (built by FGE shops in Alexandria w/conventional 3/3 ID end) and WFEX 68000-68399 (built by AC&F) appear to be identical and had tabbed side sills. FGEX 39000-39299, 39800-39999 and FHIX 900-999 had straight side sills. If the dimensions work out, one could remove the rivet detail from an IM 40-23 body and then scribe the welds. After the hinges are replaced, this "pattern" could be used to create a mold to create resin welded bodies to be combined with IM parts to create these welded cars with side sills similarly cast in resin.
Alternatively, if the dimensions are the same, perhaps IM could be convinced to cut new bodies to create FGE/WFE welded and FGE/WFE/BRE riveted bodies, and with separate locking handles to permit either the ninety or forty-five degree locking handles. Separate straight and tabbed side sills could be cut and while I am wishing, IM could cut that pesky unique ID end.
Lastly, the ART model IM created could possibly be used to model the FGEX 38500-38634 series, although this may require "Archer" rivet decals to create the parallel vertical rows of rivets.
One thing to note is that with certain exceptions, I have dodged which type of paneled roof is involved. Most of the photos I have don't have a view that makes roof type identifiable, and no drawings have surfaced AFAIK of the post 1946 built cars. Plus I cannot remember when SRE replaced the rectangular paneled roof with the diagonal panel roof. I think this was about 1949. Even knowing the date, we know builders would use up stocks of what was on hand. One of the challenges with these companies and their cars is sorting out the roof types for cars built new. All of the steel rebuilds carrying FGEX, WFEX and NX reporting marks, which are not described above, were built with the diagonal panel roof.
I have sent Mike Brock an email with the 4-page table I have created covering the 40-foot steel cars owned by FGE/WFE/BRE/NX to be posted. This is up-to-date with new series I have sorted out, including the unique rebuilds FGE created. I have a second table showing the total number of steel cars within the FGE/WFE/BRE/NX fleet from 1932 to 1957 that will send Mike soon. Again, if someone has a copy of my Steel handout, perhaps they could scan that and post it as well. I cannot find my electronic or paper version. This gives a physical description of most series but not my recent sorting out.
Bob's Photo has photos of examples of many of the cars I have mentioned.