Any gun that can fire the 454 Casull can fire the 45 Colt. Now, as far as your +P and +P+ garbage, there is no such thing as a +P or +P+ for the 45 Colt. You can not take a round and just stuff more powder into it and call it a +P or +P+ round and think it is OK to do. The organization that makes the safety determination is SAAMI, which is The Sporting Arms and Ammunition Manufacturers Institute, which was founded in 1926. If you open the reference below and scroll down to 45 Colt you will see NO +P or +P+ for that round. (Right above it you will see there IS a +P for the 45 ACP.) So instead of trying to do something DANGEROUS, research things. If SAAMI says you can not do it, DO NOT DO IT!!. It does not matter if a company makes it and sells it, SAAMI says no. Besides, there is no reason to load a hot 45 Colt if your gun already fires the 454 Casull.
Now, as far as the gun, a Ruger Super Redhawk Standard will do you well. It is all set up for a scope if you want but keep in mind adequate eye relief as you do not want a scope crammed into your eye from the recoil. The Alaskan is a trail gun just in case you run into a bear, it is not all that great as a hunting gun due to the short barrel and inability to put a scope on it.