Yabbie,
Welcome!
The .30-06, .270 Winchester, .25-06 Remington, .243 Win., are all chambered in these rifles, so to your question, yes, they'll handle pressures similar to what these rounds produce.
I'd say that yes, the round you have in mind would work out. I question, though, whether the bore and twist would be ideal for what you have in mind.
I'm a bit interested in your idea, as I have a War II era (1944) "Smellie" with a rotten bore that I'm not sure what to do with. A rebore is an intriguing idea to put some life back in this rifle.
It's been so long since I've been asked, or asked myself, the question about international shipping of firearms, the reason I'm scratching my head, is because H&R has a "Accessory Barrel Program", where you send your receiver and forearm to the factory, and they fit a number of barrels, including smoothbore and rifled shotgun slug barrels to your frame for a VERY reasonable cost.
http://www.hr1871.com/Support/accessoryProgram.aspTake 'er easy, and good luck to you!