Coating does not matter. You are over thinking the process.
After you get done you are going to have to seal the welded areas inside and outside of the tank. There are several different products you can use. So your pretty coated tank is going to look like it got into a severe street fight after its all said and done. Best to just paint it afterward.
I did an 8an Return 2 10an feeds and a looped vent on mine.
[ame="http://www.ebay.com/itm/RED-KOTE-GAS-FUEL-TANK-SEALER-LINER-REDKOTE-QT-/271375403929?hash=item3f2f3c0b99&vxp=mtr"]Red Kote Gas Fuel Tank Sealer Liner Redkote Qt | eBay[/ame]