If you reload then look at the Sherman stuff.
If you don't then look at a .280AI you can buy that ammo off the shelf.
I'd say if you don't reload stick to the .270 Win or .30-06. AFAIK Nosler and Hornady are the only two making .280 AI ammunition at the moment without having to go the custom route for the non-reloader. How many manufacturers make .270 Win and .30-06? IMO if you're going for factory ammunition those two are really hard to beat.
Good idea "if" there's enough barrel dameter at the end of the barrel it's easy to do. I've had several barrels rebored by JES Reboring in Oregon, it was like $225 return shipping to my door. The rifle barrel had to be 9/16ths on the end to rebore to 35 Whelen from a 30-06. Reboring is a great, inexpensive route to go, all three barrels that JES did for me all shoot!
JES F'd up my buddies .35 Whelen, wouldn't believe my buddy either when he said the bore was undersized. Barrel split and disintegrated the stock shooting factory loads that JES told him to try before he'd look at his work again. JES never made it right, he never gave my buddy what he paid for or refunded the money. IMO when things work JES is okay, but his CS when there is an issue is severely lacking. I'll rebarrel before I rebore using JES.