Just for your information, I wrote Henry about what pressure reloads for the 45-70 were safe. I am buying one soon. Here is what they said.
We're unable to comment on handloads as their use technically voids our Warranty terms but I can confirm our model H015-4570 falls into the 1895/modern lever category for action strength.
It will safely handle all commercial .45-70 loads except those that are listed "For Ruger No 1 Only."
Best Regards,
Thomas Kotz
Product Manager/Exports
Customer Service: (866) 200-2354