The Ackley Improved Whelen headspaces on the index point of the shoulder. If the neck is the same length and starts at the same point as the 30-06, or a piece of new .35 Whelen brass (Remington is the least expensive .35 brass) it is an improved Whelen. If the shoulder is farther forward, it is a Brown-Whelen, which is more complicated to fireform brass for. For the Improved Whelen, you can use regular brass, load it and fire it. You will then eject a .35 whelen improved case, perfectly fireformed. You won't lose accuracy. If it is a Brown Whelen you will need to neck it up to .375 and then neck it back down to .358 forming a false shoulder for the casing to headspace on, and then fire it. .35 Whelen improved dies can be had from Redding, RCBS, Lyman and Lee. They cost more than the regular dies. A 1 in 16 inch twist will stabilize the 250gr bullets, and in some rifles, the 300gr. bullets, but a 1 in 14 is better. For you, it doesn't matter. You will get best performance from 225gr and 250gr. bullets for elk, moose and bear. For deer, 200 and 225gr bullets will work well at 300, 225gr Sierras will work well to 450, 500 yds. With the Improved casing and a 26.5" barrel, you should get 2800fps from the Sierra Gameking, which makes it as flat as a 30-06 using 165gr boattail bullets out to 700yds. Have a gunsmith mike the chamber and then go shooting. I use the Sierra 225gr. and the 250gr Speer in my Whelen (standard chamber) and get 1" or less groups at 100yds.