Interesting insight Rookhawk. I have had Lee FCD made for a 416 Taylor and it worked perfectly ( sent them 3 dummy loads)I'd second guess that answer.
As a Wisconsin native I can say that we're a bit of a simpleton crowd thinking of pedestrian calibers and cheap-cheap-cheap due to the prevailing scandinavian and dutch sensibilities. As such, Lee (a Wisconsin company) is beloved for their low prices but they don't get many requests for calibers that are often in "luxury" or "foreign" genres.
Bottom line, Lee makes tons of stuff that work on large bores but they never think to advertise it as such in their product catalogs. You need to look at the neck and rim dimensions of what you own and then cross-reference it to other things like Martini-Henry, Sharps, and lever gun calibers. It's highly likely they make something that will put a factory crimp on a 450-400NE.
On the opposite end of the spectrum but a similar scenario, Redding is in New York and high-end precision shooters are their bread and butter. They also don't openly state that have anything to suit nitro express guns in their catalogs. After a lengthy call with their engineers, I found a dozen shell holders and other items I needed but I had to order them as "Cheytac" or "Dakota" related products but they worked with Jeffery, Rigby, Gibbs, Holland, and other British calibers.
The only companies that actually understand nitro calibers and cater to them are RCBS and CH4D, everybody else accidentally has what we need and they don't even know it.
I'm thinking I want one for my 450/400 NE 3".
I had bought a 405 Winchester Lee FCD thinking I could make it work for the .416 Taylor. It didn't.
I'm going to try and adjust the .405 Winchester die, and see if I can make that work.