Mainecoon;
If it's a project gun, the two most obvious candidates are an AR platform and a Ruger 10/22. Both have over 50 years of history, and either can be built and re-built till he!! won't have 'em. That's if the project aspect of the itch is first on the list.
However, if the historical itch is the biggest determinator, then the field gets pretty wide open. There's all sorts of things that come to mind, possibilities abound!
Find a pre-64 Winchester model 94 and return it as close as possible to the original 1894 configuration. Or, perhaps, turn it into the rifle, not the saddle carbine. If you want to work with a Mauser, find a VZ24 (Czech action) and you can do about anything possible with it, except putting the bolt on the left hand side of the action. If you want a sweetheart that only requires love and attention, not major surgery, get an original 6.5mm Swedish Mauser. Or just find a Kimber of Oregon gun and leave it alone. If you ever make public that you "heavily modified" one of those, it's entirely possible that you could have the torchlight parade scene from the Frankenstein movie re-enacted in your own front yard.
Have fun!
900F