How fast is their turn around?
depending what you get less than a week, if you have bends or plating it takes like 2 weeks
That hole on the top of the tank is for the rollover valve, which many people gut so they can fill the tank without the nozzle kicking off all the time. Last time I messed with the tanks on my Bullnose I used some brass PEX? fittings that fit the grommet, Y'd them together and installed a filter on the end. If you use that for the send I'd add another vent somewhere at the very top of the tank. FTI there is a factory tank for the rear that holds like 40 gallons. Google F26 tank swap.
Yeah this is that tank, or the LMC version it's 37gallons. I'm going to add the extra vent like you suggested. Makes sense. I was looking on my diesel and the vent goes into the fill port so I may try to find a diesel filler and do the same to this truck.
Diesel oem: