Fortepianos are definatly rare to come across especially originals, fortunatly im lucky enough to work on them on a regulare basis. First thing you need to do when you come across one is to find out if it is original or a copy. Original
ones need to be handled with special care you cant just jump in there and throw on any old temperment and bring it up to standar pitch that could cause srious damage to the instrument. If work needs to be done on the action that is something I would strongly recommend only a true professional undertake, these are very delicate instruments any changing of historic materials to modern materials can effect its value as an instrument and as an historical document. Copys on the other hand made in more recent times have been constructed of more modern materials and are structurally stronger, I would suggest tuning it to either 415 or at the extreme 435 use your decretion. Historically it probrably would have been well tempered ask the customer what he or she would want. Otherwise handle a fortepiano like you would a harpsichord.