All O-200's have a 6 quart capacity tank. Some C-90's did also, but most had the 5 quart tank. The actual marked capacity and the configuration of the fill neck and dip stick are airframe specific.
That said, all tanks will fit all engine cases, but you may find the wrong ones interfere with engine mounts, cowls, exhaust, etc. For example, Ercoupe tanks have the oil fill neck on the left.
That said, the C120/140 setup is not real particular about tank configuration and many different tanks will fit just fine.
21st Century words by Joseph Sobran
Need - Wanting to get someone else's money.
Greed - (Used to mean what need means today) Wanting to keep your own money.
Compassion - A politician's willingness to arrange the transfer.