1981 f250 2wd long bed with 4.9l i6
 

https://cimg9.ibsrv.net/gimg/www.for...e8c55000e1.png
Will this line work?

It says it is for a v8 not the 300 six.
Are you looking for the line from the pump to the front / side tank?
or
The pump to the tank switching valve?
or
The pump to the rear tank?

Is this for a 100 point trailer queen never to see the road or looking to replace a leaking line and get it back on the road?
If the later then I would hit up Ebay or Amazon for a coil or 5/16" copper / nickel tubing.
If you dont have a small tubing cutter pick one up and maybe a tubing bender but you should not need the bender and the tubing is easy to bend by hand.
Being C/N it will not rust out like the factory steel one.
Dave ----

For some reason it made my post into two different threads. I’m trying to replace the hardline that runs along the frame. I know it says it’s for a v8 I didn’t know if they happened to be the same my truck has a single tank

Make your own line. Much easier.

If I run copper nickel line how do I make my connection to the rubber line just use hose clamps?

yep just like the factory did.
Dave ----

You may find local help at the auto parts store. My local NAPA guys knew exactly what I needed, it's not like that are not a lot of these old trucks around, that people need to fix.

Yes, that is all you need to do. The copper/nickel is soft and easy to run and bend. And it will not rust. Some people take their brake flare tool and make a small bump on the end of the line for the clamp to hold onto. But I never did it and never had a problem. If you have a mechanical pump on the engine, the supply line will have suction. If you have a small electric pump at the rear, you will not have much over 5 psi on the lines and the clamps. I have used this method with a fuel injection system with 40 psi on the lines and never had a problem with it flying apart or leaking.