I need some advice regarding fuel caps for my 1965 Cessna 172F with regular stock 19 gal twin wing tanks. I know that there is a crossover vent tube in the fuel system and I believe Cessna vented only one of the caps.  However I have heard that for non-acrobatic flying it is better to vent both tanks so as not having to rely on the crossover vent tube. But I have also heard that the vents allow moisture into the fuel system in a plane that is known to hold moisture in the fuel tank baffles.  So my question is; would you install both vented caps or one?  And where can you buy these caps as mine are old and nasty.  I've checked Aircraft Spruce, Chief and others and can find no caps listed for this plane.  They are standard type bayonet caps with chains.

A big thanks to all who have replied to this "newbie's" questions.  My son and I have worked all winter restoring this plane and couldn't have done it without the expert advice we got at this site.  We just sent in out dues and are looking forward to learning more.