The main thing I found out with the .45-70 is that you really don't need smokin' velocity. It's not going to be a flat-trajectory rifle in any guise.
300 grain bullets help reduce the recoil and are more than sufficient for pig, black bear and deer. If you want more penetration, an LBT hardcast around 425 grains is up to the job, and if ultimate penetration is needed, go 500+ grains.
My opinion is that around 1800 fps with the 300s, 1600 to 1700 with the 425s, and 1250 to 1550 with the bigguns is enough, though the latter two weights at the higher velocities will result in heavier recoil.
I've gotten to where I really don't like the heavy recoil. It's just not worth getting beat to death for a 150 lb deer.....
Your 350s ought to fit into the scheme of things just fine. Given the size of animal you have stated that you'll be shooting, gummy tips oughta be just fine.
Enjoy your rifle!
