There are two relatively well priced 350gr loads made by HSM for the 45-70 that are pretty close to the claimed performance of the Hornady 350gr .450 load. Also a decent, moderate load with 400gr JFN among the several 45-70 loads they make. PGs 59 & 60 on their online catalogue have the 45-70 stuff.

http://thehuntingshack.com/catalog/retail/ProductList.pdf

 

But, the answer if "no" Hornady will not offer a 350gr flatpoint bullet load that equals the 450 Marlin load. It is very easy to duplicate that load at home if you get into reloading.

 

.

The answer is "No". There are too many old 45-70's around that could handle the pressure. That is the reason for the 450's existance.

 

336ER

Thanks for that link, they do have some pretty interesting ammo listed.
Frank