I'm in that process right now for a change over to FI. I've converted the stock feed line (3/8" and 6AN) to a return as Jay suggested and have run 1/2" aluminum hard line and 8AN lines for feed. As jay said, the tank is my hold up as well. Mine is an aluminum tank with nothing but a couple of tubes welded into it. I don't even know what size those tubes were but they were smaller than 1/2" and larger than 3/8", probably some metric size. Maybe Jay can shine some light on that. To fix that choke point, I ordered a couple of 1/2" NTP weld-in bungs from Summit and was supposed to pick up the tank with the new bungs and pickup welded in today. Alas it was not to be. I've also had to make a few changes to how things were routed. The high pressure FP requires the use of a pre and post filter which made me put the pressure line in on the passenger side for packaging reasons. Thus far the line installation has turned out pretty sanitary. I'll try to get a couple of picks of what I've done so far.
UPDATED w/ PICS. From the back, forward;
What my tank looked like:
Looking at the frame cross member just forward of the diff at the pre-filter, HP pump and fittings to go over the frame to the hard line:
Right side frame rail, hard line attached with Adel clamps from pump:
Hard line attached to HP filter ( secured with hose clamp and metal screw to frame rail)
Hard line from HP filter up to 8AN line at throttle body:
Sorry for the crappy phone photos but that's all I have for now.
Steve