No, you cannot simply "flip" the PTO, the gears would not lign up correctly. I have seen some say that you can pull the gear and shaft and reverse them inside the housing and then do it.
A simpler option would be to get a dual output PTO. It will bolt tight onn and you can power your front winch and a rear accessory at the same time with it. I have one for sale if anyone needs it. I also have a PTO pump from an old dump truck and several Duece front winches.
I have been thinking about this myself because I would like to get a M870A1 trailer which folds down flat for self loading, but it requires a rear winch to assemble/dissassemble like the truck that TOPO has shown.
Derek Taylor