Gas Tank?

[88Sunbird4.3L]

Hey.. I have an 88 Sunbird Corsica 17.5 w/ 4.3L omc. Just wondering where the gas tank is located from the factory. Mine is on the right hand side (if looking at the front of the motor) of the motor. Its just held down by a couple of L bracks and screws. Its nice that its easy to access, but its really in the way when doing any repairs or installing manifolds on that side of the vessel. Just wondering if this was an aftermarket installation. Thanks!