For those of us modeling RR's east of the Mississippi River, I suggest the following in styrene.
The most numerous wood sheathed MDT reefer (I think it is classified as the Type 4 by Roger Hinman)
The ubiquitous AAR standard offset hopper done in a way that permits production of the various ends and sides.
The PRR K8 stock car with ends permitting the L&N and I believe ACL versions (I have not unpacked all of my photo albums but I know at least two railroads duplicated the Pennsy's Pratt truss stock car side configuration)
InterMountain do the Insulated Tank for their ACF Type 27 Underframe.
Someone offer photo-etched dome platforms for the ACF Type 27 8K and decals for the cars with these platforms.