Bowen Custom converts the Redhawk to .454 Casull and .50 Linebaugh. The Redhawk should be able to handle hot .45 Colt loads. If you're gonna reload the .45 Colt should be an excellent choice for you. I don't know how experienced you are as a reloader but use common sense as always. People have blown up Redhawks, Super Blackhawks, and Freedom Arms by going too far.
http://www.bowenclassicarms.com/NEW/RugDAbigbore.htm
Oh, BTW azredhawk44 here be my Redhawk 5.5" .44 Magnum. I could have gotten a used S&W 29-1 for the same price but I liked the Redhawk better. The trigger? I don't know what people are complaining about. At least as far as recent Rugers go this trigger is better than a S&W 686P and 60 I bought in the last 2 years after some dryfiring with snapcaps. And its as strong as an ox. Very happy with my choice. And as you can see I got the Hogue bantam grips they put on the 4" version. The grips are working out perfectly for me.