Seeing the thread about Hart Square got me thinking, since I went through something similar on my own place a few years back. The original porch had rotted through and I wanted it to look right, not like some lumberyard special slapped onto an old cabin.
First thing I learned the hard way: match your wood to the era, not the big box store. I found a local sawmill that would cut me rough poplar in random widths, and that made all the difference. Machine-milled uniform boards read as fake from thirty feet away. I also laid the flooring with wider gaps than modern decking, which is what those old builders actualy did for drainage. For the corner repairs I studied how the original joints were cut before touching anything, then practiced on scrap untill I could repeat it. My chinking on the wall section I patched was a premixed product from a masonry supplier, and honestly it beat the old sand-and-lime mess my grandfather used.
Took me two summers of weekends, but now the whole thing sits under a plain tin roof with a couple of rockers on it, and folks assume it's all original. Slow is the whole trick.