Southern yellow pine would be a good choice, though soft and would show dings a lot. Cedar would be similar. White oak would be a good choice, as Hambone said. There is a grade of Oak that is for trailers, this is the material we used in our Model A 8 years ago-still looks great! The cost, from the mill where our cabinet shop gets material, would be about $300 for 5/4 white oak 16' long. Most all woods are available 8, 10, 12 and 16' lengths. As far as thickness goes, 4/4(four quarter) is 1" thick in the rough and will plane down or clean up at 3/4" thick. 5/4 will cleanup at 1", 6/4 will clean up at 1-1/4, and 8/4 will clean up at 1-3/4". There are different grades of wood as well; for the most part they are as follows:
F&B - face and better, best quality - no knots
1 Common - few knots, tight, should not fall out of the board.
2 common - more knots, some maybe loose and fall out of the board
trail floor - tight knots, other defects throughout the board
Any wood you use you'll have to put a finish on it or it will check (split),cup, and turn grey/silver .
Hope this helps. Let me know if you have other questions.
