gypsypit and spasm3, I'm sorry for just seeing this now. I haven't been back here, even though I owe this board a lot for helping me through my mods. Sorry gz250.com!
It's a harley P Nut tank, holds 2.2. The bigger ones look way too big for the bike. With a free flowing air cleaner and straight pipes, I just make sure I stop for gas every hour.
As for the year, not really. The petcock, it's what came with the tank when I bought it and I'm not sure that the old one will fit, unless cut the opening to fit it. Didn't want to go through that trouble. I just got a set of plugs from the auto store and called it a day. It's really easy! Let me know if you have questions, I'll try to help you out as best as I can.
Ken