I don't know what express sights are. If it's the rear sight the hole spacing on the mounts is the same for most models of Diana rifles and has been the same since the sixties or before. The front sight mount has varied significantly among the models and through the years. I believe the 350 has a dovetail mount front sight as was used in the sixties. Since the 460 sight is quite different I expect the AM03 sight would be as well. Good luck.
Wes,As I am sure you know "express sights" are not particularly accurate. The are mainly used for short distances and quick acquisition.Williams should have what you are looking for:https://shop.williamsgunsight.com/ecommerce/c/long-gun-sights-844if not there, then their military sights section. Have you tried the ZR mount on your "Bucking bronco"?-Y
I wasn't really sure where to post this, the optics gate seemed to fit as close as I could find LOL. I love the express sights on the rifle I mentioned in the title and I was wondering if there was a way to mount them or an aftermarket version of them on a Diana 350? Thanks guys.