Basically as it is right now its
57"(l) x10.75" (d) x 10"(w) at front and 9"(w) at rear ~ 25 gallons
But need to remove the two frame notchouts (~ 10"[w]x6.5[l]x5"(d) ~ 650 cubic inches or call it 3 gallons. So a 22 Gallon tank as it stands.
Really pushing the boundary of depth to ground clearance as well as its tucked right up behind trans crossmember as well as rear axle.
Some other dimensions and sizing to play around with
