They could supply 5/16" line and fittings but it wouldn't flow as well and you would risk damaging the barbs on the Mercedes fittings when you tried to remove the stiff factory lines. After converting several Mercedes, I compleatly agree with Frybrids choice. But I think that their documentation as a little vague on this point.

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Ron Schroeder
'85 300 Turbo Diesel 2 tank WVO
'83 300 Turbo Diesel 2 tank WVO
Some former WVO vehicles since ~1980:
'83 Mercedes 240D
'80 Audi 4000D
'83 ISUZU Pup
'70 SAAB 99 with Kubota diesel
'76 Honda Civic with Kubota diesel
'86 Golf
Several diesel generators
All with 2 tank WVO conversion
LI NY