A friend of mine has a 408 LS1 making 500rwhp NA through a th400 and is running a single 255 with the upgraded wiring with no problems (racetronix). He has been running it for about 5 years now. I am in the process of finishing up my solid roller 383 LT1 build (prob 575 crank HP max when dialed in) and am going to use the same setup with 43.5 psi and 55lb injectors. I talked to Lonnie at Lonnie's performance about the dual pump setup and he talked me out of it as he stated the 255 pump with upgraded wiring would support ~650 NA hp and about 500 FI due to the inceased BSFC of an FI engine. BTW, the 340 is the same 255lph walbro pump but has a higher pressure efficiency range (nevermind...seen you were talking about the aeromotive). Lonnie also stated the fuel lines would need to replaced with bigger lines than factory when using the twin pump in order to get to the 1000hp support figure of the system. I assume to get the benefit of an Aeromotive 340lph pump you would also need to upgrade the 3/8" factory line.
If I was going to upgrade the enitire fuel system I would go with a Nasty performance setup as they are a drop in aftermarket fuel system for our cars with all the parts. I will most likely go with this setup in the future but seeing how my friend's car performed making more power than my setup will with a higher fuel pressure used I think I will be fine.
96Z solid roller 383 in the works
old 355 A3 combo:
11.4@118 NA 1.579
(150)10.3@129/1.437 (200) 10.2@133/1.592
Sold-02Z M6 Cartek 2X bolt ons
12.6@117 2.333 60'