most good quality fuel injection lines have a inner liner that resists bio-D. (gates and goodyear, to name a few) this will cost more than regular fuel line, but less than 100% viton.

5/16 should work. use the good oem style clamps- you can get them most places as fuel injection clamps.

good luck

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1984 123.193 372,xxx miles, room for Seven.

1999 Dodge Durango Cummins 4BTAA 47RE 5k lb 4x4 getting 25+mpgs, room for Seven.