Project64k is outdated and only properly syncs very few games. See Mupen64 for better compatibility rate.
Official Download: http://www.mediafire.com/download/bra4tcaji599i4v/Project64k.zip
Project64k is only suggested for emulating Mario Kart 64, Super Smash Bros 64, and Super Mario 64 Multiplayer Rom Hack online.
For games like Mario Party, Goldeneye, Perfect Dark, Diddy Kong Racing with Save Support use Mupen64. It is highly recommended over PJ64k, but PJ64k seems to be the emu of choice, despite only running about 4 games in total correctly over netplay.
For most the 'best' netplay with no desyncs, use Project64 1.7 with AQZ Netplay input. Which a tutorial and download bundle can be found below. (Note: AQZ works with Savestates and each individual player having the same emulation (saves, and cheats) information as each other, as well as someone Port Forwarded to host the server, or using a VPN like Hamachi)