According to Hodgdons website 50gr of IMR 4198 is a max load for a levergun so they're likely ok to shoot in your rifle, However,

we're always cautioned to Work Up To a max load when changing Anything, including, primer, powder, bullets, you've changed the Rifle. I'd work up to a top load for That Rifle.

Also, the Speer 350 is a longer bullet from the crimp groove to the tip of the bullet so I doubt the cartridges will feed in a levergun, if you loaded them in full length brass. They'll be a bit long but as you said were fine in your #1.

I've used Speer 350 in a Marlin 45-70 but I had to load them in Hornadys 45-70 brass, they're shorter but that's a different situation.

"Camping places fix themselves in your mind as if you had spent long periods of your life in them.
You will remember a curve of your wagon track in the grass of the plain like the features of a friend."
Isak Dinesen