Montanan, there are a few things you need to know. First, some of the velocity data is a bit suspect in that article. The 336 action is not up to the pressures of the .358 Winchester, IMO, and don't be misled by the fact that .307 and .356 pressures are listed at 52,000 CUP. This leads to the mistaken assumption that this is the same pressure as the .358 runs at. All CUP means is the figure for pressure is undefined, and most likely much lower than .358 levels (Keep in mind that psi figures have never been published for the .356). Remember-traditional leverguns have poor safety features in the event of a blown primer, and you need more margin in working pressure. You should consider equalling .356 velocities and no more with the 336. Most likely, this is around 46,000 psi, and plenty high enough. The true .358 loads go well past that.
Documented firings of high pressure loads in rear locking guns such as the Marlin and SMLE show short case life and head separations when they are loaded to bolt gun levels. This is why the leverguns are loaded to lower levels in the first place. There is just too much spring in the bolt to withstand 62,000 psi, which is front locking boltgun pressure. It should be properly confined to guns of that type.
Finally, the other thing the article neglects to tell you is that none of the 200 RN's or 250 grain bullets will work through the action. This is because the overall length of the cartridge must be below 2.57 inches, and all of the 200 RN's and 250's exceed that when crimped in the cannelure in the .358 case. Since bullet diameter gets smaller ahead of the cannelure, crimping in a new location closer to the bullet nose is not an option, because there would be a gap between bullet and case mouth, reducing neck tension. You can't crimp effectively on reduced bullet diameter. Notice how you didn't see any other bullet than his 147 grain 9mm bullet (a crappy choice for those velocities, unquestionably. Talk about a blow up bullet) loaded in the case?
If you decide to check my assertion and try loading a round over 2.57", be prepared to remove the lever and bolt to get the round out of the gun.
I suppose you could enlarge the ejection port, but the carrier may need to be modified too. He didn't say squat about that, and I suspect there's a lot of other things he hasn't told us. I would be very, very interested in case life produced with his loads (notice that he didn't give us any?) Also, like Bman said, the claimed velocity was for a 26 inch barrel in his table. A 20 inch will be substantially less. His pictured gun was a 20 inch. If he's equalling Whelen velocities with 200 grain bullets in a 20 inch barrelled 336 he's a fool.
If you like the 180 and 220 Speer, they will work. If you like those bullets and are willing to load to .356 levels, then you may be in business. If you want to duplicate .358 pressure levels and use 200 RN's or 250's, you're pursuing a dead end. Case life will suck, and you'll be beating the gun to death. Your eyeballs could be next.
Sorry to sugarcoat it like this, but that article is one of the most misleading bits of drivel posted anywhere.