A couple of thoughts:
1) As pointed out, the .30-30 will do what you're looking for as is. If it ain't broke, and all that.
2) If you just want to rechamber it because you can, a .30-30 AI chamber can fire factory .30-30 ammunition with no ill effects. In fact, that's pretty much how you form brass for the AI.
3) While the .309 JDJ is a fine cartridge (I can surely understand why you're considering it), you're looking at dies in the neighborhood of $70, a multiple step case forming process (at least I assume you don't neck straight from .429" to .308"), plus the cost of the rechamber. It is definitely different from the AI, though.