Redoing everything in my 87 tII starting with the tank and moving forward . My goal is to put down around 450 hp at the wheels and still kinda street it . Gonna run stainless lines but not sure what gauge to run for it .

 

You may get stuck at the fuel rails anyways..They always seem to be smaller than the biggest you can do on a fuel system.

 

6AN is about right.

 

Easy rule of thumb for fuel line sizing from A. Graham Bell:
1/4" OD (-4 AN) - 165bhp EFI, 110bhp Carb
5/16" OD (-5 AN) - 300bhp EFI, 200bhp Carb
3/8" OD (-6 AN) - 500bhp EFI, 335bhp Carb
1/2" OD (-8 AN) - 1000bhp EFI, 675bhp Carb

To address the fuel rail issue mentioned in the first response, just run the rails in parallel. You can also use two fuel lines if you wish, and a lot of people do this if they want to use two low-budget in-pump fuel pumps as opposed to one large external fuel pump.

Since 450hp at the wheels is roughly 530bhp at the flywheel, a single -6 pressure line would probably work OK, especially if the car did not see max hp for very long, such as in drag racing. A single -8 with a Y feeding parallel -6 rails would relieve a lot of strain on the fuel pump, but it may be overkill unless you are using an aftermarket fuel pump PWM controller.

The Aeromotive website has a nice power planner.
Aeromotive*|* Power Planner