Sorry, I don't know that mount system and don't have a .454 Casull, so I can't give you advice on them from personal experience. I go from .44Mag/.45 Colt to .45-70 Contender.
I can give you a bit of advice on the red dot sight. First off, decide for yourself how long (how many shots) you think it ought to last on your gun. Then go see if you guessed right...
Somewhere around 15 years ago, I got a cheap red dot ($35 IIRC) don't remember the name right now, BSA, maybe.., anyway, got it basically to see how long it would last before breaking...Its on my .45-70 Contender and so far, has survived several hundred shots (standard ammo) ok.
I don't shoot groups with my single shot (bit of a waste of time and ammo, I think), but I do have it dialed in so I'm on the "dot". When the sun is just the "right" place, even dialed up to brightest, the dot isn't easy to see. The rest of the time, it does fine.
A higher end (more expensive) red dot sight might not have this problem, I don't know.
A couple of points to remember, always, always make sure the sight is OFF when you put the gun away. I was careful to do that, but even so, batteries don't last forever. What ever "coin type" battery the sight uses, get a couple packs of spares, store (and carry) one set with the gun.
IF you don't, Murphy will be your shepherd, and the exact one you need will be the one that WalMart is out of, or that the back country store doesn't carry.
Check the sight operability when you pack your gear, and have a spare battery stashed somewhere it won't be forgotten at home. Other wise, you will have a nice 0 power tube to look at your trophy through, if Murphy has gets to do his mischief.
I'm not unhappy with mine, it is easier to use than a scope, and I too am at the point where iron sights aren't as easy to use as they used to be...
For most of my life I was opposed to anything battery powered on my firearms. Today I have learned that they can have a place and work well within that place. Just remember the limits, and make allowances for them.