The only big American guns that made it to plastic that I am aware of are the AFV club 155mm and the 8 inch howitzer on the same carrage. I could be wrong as I am just getting back into the hobby after a forced break of several years.
Didn't Verlindin have a resin kit of the 240 mm back in the '90's???? I don't know how accurate it was, but I seem to remember that kit being available.
BTW, I too am extremely happy about the current availability of Allied armor. As always, we all have our pet "wish the major companies would come out with this" project.