Yes the Stevens has the barrel nut. I figured 2000 was mild for this round, especially considering it is not limited like the revolvers are. At those speeds you WILL have to consider bullet design. Might just have to have someone build a new bullet for ya!
This could be the start of something big. Just keep the twist rate in mind, if you decide to go up to the heavier bullets. Marlin used the 1-38 on their 44 mag rifles and when pushed to NORMAL 44 mag velocities, a 270gr bullet was about tops. However if you pushed the speeds up it will probably work.
One thing to keep in mind that a lot of small bore (under 35 cal) rifle owners never experience, is that big bore gun work best with heavy for caliber bullets. Example, the 45-70, in a modern Marlin rifle, can push the 300gr bullet over 2400fps. However, the same rifle pushing a 430gr bullet at 1800-1900fps will get better penetration on big animals, like moose or elk.
Guys have taken those guns to Africa and dropped the biggest animals on the planet with slow moving heavy bullets. I'd bet you could push a 300gr at 1800-1900 from your round, and the long 300gr, .429 bullet would plow through anything on this continent.
That would be an awesome pig gun. Keep the 265gr Hornady bullet in mind also. Hornady made it for the 444 Marlin.