I hear you on re-purposing stuff. Our evaporator is an old oil tank also, although I did weld up an arch inside to force heat up closer to the pan. The firebrick helped a lot also. I'm considering AUF, but the stack temps already push 1000 degrees at times on natural draft, so we boil pretty hard the way it is. Sounds like you are getting a drop flue pan. Watch your sap levels....drop flues can be unforgiving. Wise choice on the float box with that configuration.
I wasn't sure if Ontario was under the same strict policies as Quebec is. The Federation doesn't play around. I hear they will post guards at your property to enforce the regs.
