I think you're making a good choice Ken with the 1" x 42" .45 GMB...
As for style,,, geez,,, chunk guns are so danged ugly I'd venture to say they are based on just about every style out there in 'yesterdays' world.
I do believe a favorite however is the fullstock with not much drop as it is much more friendly when it comes to recoil on the shoulder area, and you certainly don't want a sharp cresent buttplate.
The cant block built into the muzzle end of the full stock I feel is a favorite by many chunk gun shooters. Were I to do a full stock and base it on a longrifle design, I like the Dickert with no more then a three in drop, and fatten up the wrist just a bit.
Let me post a picture of my halfstock here in a few minutes. Give you an idea what I'm using (but I'm not completely thrilled with it)... I should have built fullstock...