Hmm, you used one bullet, the FTX, and it penciled through the animal. So, the logical thing to do is rebore (actually rechamber) the barrel? There are other 35 caliber bullets designed to expand at the more sedate speeds the 35 Rem generates. Its a lot less expensive to switch projectiles than to rechamber. Also, as someone already pointed out, you selected the cartridge due to its light recoil. Punching it out to .358 Win is going to completely undue that.
I'd suggest perhaps a 180 grain bullet at slightly more velocity. Recoil will be about the same as it is now with the Leverevolution ammo.
