I found that if I removed the little brake line clip, Dorman 800-015, and pulled the "L" shaped connector off the FSV, that a 3/8th rubber hose would slip right onto the nipple coming out of the FSV. I tightened it down with a regular hose clamp. I didn't change the return line, but I'd bet you can do the same with that and a 5/16th rubber line.
In the picture below the supply line to the engine is the closer one of the upper pair. You can see an example of the clip more clearly on the line coming out the bottom of the FSV, and you can see another view on the line going toward the rear of the truck. It's the part with the pointy shaped piece flush with the fitting.
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