Replaced Duel tank With one, Do i need to seal up old one?

Both tanks leaked, Replaced Front, Took off Rear, Wire Wheeled and Brushed all rust off and used Ford rustoleum Metal Primer -

Do i need to do some thing with fuel line that is now not hooked up to any thing?
Or if i do end up getting this thing ever is it going to leak out fuel in back?
or maybe this is why my truck will turnover but not start?
Also i don't see any gas leaking out of the lines,
But that might change when i do get it running?0_o
Ford f-250 -1991 - 4.9l

Put some gas, or starting ether, in the intake, and if it starts for few seconds, that will prove it's a fuel problem. I would try closing off that other fuel line. Perhaps with a couple of brass fittings that form a cap at the end of the line.
I don't know if there's any other complication here. It's possible.
I hope someone will fill us in on the fuel tank plumbing.

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