I think I've decided on a Ruger No.1 Tropical, or either the Ruger Safari Magnum chambered for the .458 Lott. I'd prefer the No.1, mostly because I've shot a Troical before in .375 H&H and I like the feel and blance - a lot! The Lott is more affordable to shoot, and I can use some of the bullets I already have for reloading at velocities not attainable in the 45/70. I'm not recoil sensitive, so I'm thinking it won't be a problem that I can't overcome and the power is there to end a confrontation with a big coastal brown quickly - without bloodshed, mine that is.
Thanks to all for the comments, suggestions and advise. It was all helpful and much appreciated. Any comments on my choice will be more than welcome. Thanks!