I'll say up front that I haven't been boar hunting. YET. But, if I was going to make up the ultimate boar rifle, from what I've read and seen and heard, I think that I'd go with a .35 caliber too. I think that a Marlin 336 is one of the best handling rifles around, perfect for nosing around or hunting from a stand. The .35 Remington loads from Buffalo Bore ammo use a 220 gr JSP at 2200fps, a much stronger load than the other factory loads. I think that it'd swat a boar (or black bear for that matter) with ease, probably out to 200 yds, and most of what everyone says is that boar hunting is usually a short range proposition.
The .358 Winchester, .35 Whelen, and .350 Remington Magnum should all be superb. Of course, unless you got a 7600, Savage 99, or a Browning BLR, those are all bolt action or single shot rounds. Then there is also the .444 Marlin, and the loads from Hornady, Buffalo Bore, Cor-bon and other premium (and semi custom) make it a hammer of a round.
I thnk that I'd get a Marlin Lever action in either .35 Remington (the lower recoil offering) or .444 Marlin if being slammed a bit doesn't bother you. I can shoot faster with more accuracy with a lever than a bolt action, if things get dicey. Throw a fixed power 2.5x or a low range variable on it, 1-3x, 1.5-6x, something like than, and get some pork.