Is your Deerstalker the stainless or blued model? The stainless version has the same 1 in 48 twist, but it has shallower grooves, which according to Lyman is better for shooting conical and saboted bullets.
I have the stainless Deerstalker in 54 caliber. I can't really tell you what works best in it yet, as I have not done enough testing with different powder and bullets. Right now I am using 2F Triple 7 with a 330 grain Harvester hard cast saboted bullet. I got acceptable accuracy out to 100 yards with 95 grains of powder.
When time and money allow, I will be doing more testing with different powder (Pyrodex, 3F Triple 7) and I would like to try the 325 grain Barnes Expander bullet.
But for now, with deer season beginning in less than 4 weeks, I probably will not change anything. I would rather spend my time scouting rather than shooting. I think either of the bullets you already have would be good as long as they are accurate in your rifle. That Hornady 425 grain would really work well on elk. I would start with 80 grains of powder with that heavy bullet and work your way up to no more than 100. Good luck and welcome to the forum. I'd definitley be curious to hear what you end up shooting.