Re: Detailing for early tank cars
No shortage of options of "horribly overscaled" early tank cars.... might I suggest the Funaro & Camerlengo type 7 ACF kits with High Walk?
For HO detail parts, Jason over at Owl Mountain Models makes a useful assortment of M.C.B. and Frangible tank car dome vents, and various parties make quality brake parts.
But alas - I share Charlie's pain.
I'd love to see N scale get, say a "High Walk" 10K gal ACF type 7 (like SD&AE MW 1021 which still stands to this day - in the wild, trapped but not forgotten - in Jacumba, CA).
Still, there are a few obscure kits for tank car diversity for N scale guys. Not a "high walk", but Dick Billings of Fine N Scale makes a resin cast of an early high dome tank for use on his 35' truss rod flat cars. It's a bit generic, but I'm working on a pair now as "Pease" rebuilt as CS-12A cars for SP service, with hope to try using decals designed by Tony Thompson, now produced by Tichy. These FNR-2104 castings - if with a new dome - might even be a better stand ins for early AOX tank cars used privately, but apparently saw use in SP & Santa Fe (Tk-C & D) service (see Tony's SPFC vol 5 p 215).
Speaking of Santa Fe in N scale, while not truss rod, you should also be aware of the wonderful early AT&SF Tk-G to Tk-J kits by Dirk Jan Blikkendaal in the Netherlands (https://atsfnscalemodels.com/projects/tankcars%20class%20tk-g%2C%20h%2C%20i%2C%20j.html)