82 Dually converting to round side tanks... help needed

[nicke]

Hey guys, I have a 82 c3500 dually chassis that I'm working on right now and building out a flatbed for it. I'd like to ditch the complete dual saddle tank setup from this rig, and I'm looking for options to run round, aluminum tanks like you see on a semi, but smaller (I'm thinking dual 20 gallon tanks).

Did the factory do anything different with the fuel tanks on factory equipped flatbeds of these years?

Any idea what the original fuel gauge resistance is?

Thanks!