Fuel lines and fuel return?
 

Do I need to make a new fuel return on my stock std 74' fuel tank for using an injected Turbo Ecotec? Replacement tanks? Kits?
Also what size fuel lines to I need to run with a 450 hp inline 4 with 18 lbs boost?

You might find some info on this thread
http://www.volkszone.com/VZi/showthread.php?t=159276

I've got size 8 feed to the engine and size 4 return but the engine is only expected to product 180hp. I would have thought this would be large enough but your main consideration has got to be the size of your fuel pump to delivery enough. My feed comes from the bottom of the tank and the return has been welding in on the left hand side at the lowest point.