I see just worried that 8mm OD will be around 6.4mm ID and not sure if that will be ok with a 300bhp forced induction car running a 255 walbro fuel pump.
From what i have seen on alot of the skyline owners clubs and forums 5/16 (8mm) id is good for around 300hp
"Up to 250 HP = 5/16" or -04 AN
Up to 375 HP = 3/8" or -06 AN
Up to 700 HP = 1/2" or -08 AN
Up to 1000 HP = 5/8" or -10 AN
Up to 1500 HP = 3/4" or -12 AN"
Something like this..
http://www.ebay.co.uk/itm/Aluminium-...item416896387e