Hello, Dave, The SCC allowed claims for Alabama have been recently microfilmed and are available for purchase from the National Archives. (When I did my research they were still in manuscript form only.)There is a nice guide to this microfilm, as well, that one could have photocopied by NARA--it gives the names of the claimants on each reel--they are organized first by county and then alphabetically within the county. (Be aware that some errors were made in assigning people to their county of residence--also, if the person had moved to a new county after the war, the claim will be filed under that county, not the one in which they were living during the war. It's important to check Gary Mills' master index to make sure that you can find the individual you are seeking, if you are looking for a particular claimant.) I'm not sure if any libraries are lending copies of this collection yet, but that would be a less costly way to see them.
I found the papers of the Alabama Governors and the Freedmen's Bureau particularly helpful regarding post-war Republican Party organizing, but it was nice to have names from the SCC to correlate with the various letters and reports to/from governors. Some claimants did discuss their Republican Party activity, but this occurred randomly, simply because the SCC did not ask standard claimants (i.e., the ones not giving testimony in person in DC) direct questions about their post-war political allegiances. If such information appears in the testimony, it was offered voluntarily by the claimant. Some of this is pretty juicy stuff, though, and I write a good bit about it in the last two chapters of my book.
Beyond 1874, I am of little use to you for particular references to sources, simply because that's the cut off point of my own research--sorry! Best wishes, Margaret