Well, you already have a short action Stevens. You could change it to a .260 (or AI version) but you would have to change the bolt head out and depending on the magazine, there may be some feeding issues. Not sure how your Stevens is set up (thinking blind magazine, so may need different follower). Any of the other SA cartridges (.308 family/.473" case head) should work.
Of course, in order to get the pre-fit barrel screwed on right you're gonna have to look at a barrel nut wrench, barrel vise, action wrench and go, no-go gauges.
This is all doable for a lot less than a full blown custom and YOU did it. Just saying.....