Current production P-35's mainly NEED a trigger job and a good dehorning/carry-bevel package. Depending on the shooter's hand and grip, the hammer may need to be modified to prevent hammer bite. I also prefer to have the magazine disconnector removed as well.
"Need" aside, they can also benefit from aftermarket sights. Heinie and Novak make nice ones.
The older P-35's, with tiny sights and safety, NEED new sights and an aftermarket speed safety (or ambi, for southpaws).
Brian Bilby (www.45acp.com) does superb work, as does Kurt Wickmann (www.kwgw.com) and Novak (www.novaksights.com).
Rosco