Given you have the lines in "stock", I'd plumb the feed w/ the 1/2" [-8], and the return w/ the 3/8 [-6]. 3/8 and 3/8 is also OK, IF you keep the FWHP at a "street" level, on gas. [E85 is another story]..[And, we all know how that works!. I ran 26# on the street in my turbo Buick!]
I'm betting that you will be turning the boost up, so those lines should be good to go!
If the pump does not have a filter sock on it, I'd use a 100 micron s/s filter, to the SS line, then a 40 micron SS filter up near the engine.
Also, if you are hooking up to any lines such as the stock tank, use the metal retainer quick connects. The plastic lock pieces have seen some failures.
Russell makes them. Here's some pt #'s.
644113 5/16"
644123 3/8"
Also, while doing the plumbing, I'd suggest you add in a pressure transducer and use it to log the fuel pressure. There's a tutorial on how to do this.
I drilled and tapped the spare regulator port plug, for mine.