I have OSB in my 86 MH. You might want to consider a wood laminate flooring product instead of toungue and groove. While my OSB as in good overall shape (no rot) but was less than perfectly level. We were originally planning on a commercial tile installation but decided the OSB wasn't level enough for it.
We installed laminate and found that the "floating floor" was very forgiving and easy to install. I think if you secured real flooring you could end up with some creeks in your new floor after a while.
Many others have also found Pergo (or similar) to be a good lower cost, easier to install option for wood flooring. The cork also looks great.
FYI - I bought my flooring from Sam's Club. It called UniBoard and it was about $1.10 per square foot. Came in Maple, Oak and Cherry. Bought 100 square feet or Maple and installed it front to back in about ten hours.
Link to our installation
Another 345 owner installed laminate up front and carpet in the rear and it looks great.
Good luck with whatever you decide and post pictures of the before and after!