I tried searching for an answer but couldn't find one. Restoring an 85 XtraCab 4wd painted Army Green to match my 22 Tacoma. I'm down to the fuel hard lines. There's 2 (vent and return) that run under the cab. The pressure line runs with the brake lines along the PS frame rail. I planned on replacing all 3 with new 3/8" steel brake line. Is there a reason why Toyota ran the lines separate from each other? Could I run all 3 lines in parallel with each other either along the frame rail or under the cab? Is there a better way to do this? I have the old lines for a template and am proficient with a bender.

No reason at all as far as I know. I would keep them on the frame but make sure they are mounted securely and not rubbing on one another. Any reason for a large fuel line? Stock is 7mm. 5/16'' (8mm) is a little bit larger and easier to work with, 3/8'' is quite huge unless you're running a V8