I have the 3-gallon OMC (actually, Bombardier) Dura-Tank with a gauge. Two things (maybe 3?), the Dura-tank is the best "plastic" tank I've seen! Much more rugged than the after-market ones. It is also.....a bit pricey! YIKES! I paid around $60 for mine in 2006, but WORTH EVERY PENNY!
The gauge is, in my opinion....useless or nearly so, we have a 6-gallon Dura-Tank on our 14' powerboat and the gauge is slightly more usefull, but I still don't rely on it..... a marked wooden stick always works!
The one upside/downside to the OMC/Bombardier tanks is that they only vent in.....good, because it limits escape of fumes.....BAD, because as the tank warms up in the sun or just a hot day......it swells and the bottom bulges out allowing the tank to rock. Simply loosening the cap releases the pressure (and a burst of fumes), so I would not let that stop me from buying another! Also, be sure to use a genuine OEM connector at the tank to be sure it seals and will "lock" onto the tank connection. Also, the YAMAHA connectors look identical to OMC/Bombardier......but are ever so slightly bigger, meaning they will not seal onto the OMC male connector (discovered that while working in a marine store!)
We used to have a metal OMC 3-gallon tank (original to the 1981 and 1989 Johnson outboards we had) They remained rust free or nearly so (well, the 1989 tank did) despite being in the cockpit all summer. However, the tank was under a cover and raised about 2" above the cockpit sole. There may not be room to place some kind of spacer under a 6-gallon metal tank in the 222 fuel locker, but something like the old, plastic deck-clips (for want of a better name?) that OMC used to sell to hold their 3 and 6 gallon tanks in place on a deck would raise the tank just enough to keep moisture from being in constant contact with the botto mseam of the metal tank. I've attached a couple of pic of our homemade gas tank locker (on our old CAL 21) for referance to one reason that I see for our lack of rusting over the 8 seasons of use. The picture shows our 1981 tank I think, slight rust but not bad yet. The plastic tank isn't mine, but is a pic that I think I found on eBay prior to buying my tank at a local Evinrude Dealer.