For 500rwhp, I'd go:

Single walbro, stock lines (add a 2nd/lines if you're not going to use meth)
550 cc inj (maybe 680)
Aeromotive FPR (or whatever dependable FPR you prefer)
Methanol injection (AEM, snow, etc)

I don't see that point of the huge injectors if you're not using E85 or have a higher hp goal. Depending on your tuning, you're going to get crap mileage with 1000cc running around town too which really doesn't help.

At least with meth you're only burning the fuel when you're at WOT and the rest of the time everything's normal and efficient

 

500rwhp is near the limit of a single Walbro thus I'd run dual Walbros for safety.

 

I already have the car pretty much done. It gets dyno tuned on the 26th. I just want to make sure i could hit 500hp on a single walbro.
Mods are
Single Garret 67mm
PTE 1000
Walbro 255 AN-6 Lines
Aeromotive AFPR
AEM EMS wired for Sequential injection
Full 3in Exhuast
3in Ic pipiing
4in Inter cooler
and a bunch of other little stuff

 

One walbro is at the limit trying to keep up with 500 hp.
Cheap insurance to have dual pumps, also extra room to grow with out having to upgrade down the line.

 

Drop a MK4-TT Denso pump if you don't wanna run two walbro. It's good for 600WHP or less.

 

There's no point doing that for minimal gains when he really needs a second pump if he's ever going to use his turbo to its fullest. It's quite possible to make 500 on a single walbro, but that's near the limit. I'd add the second pump now because you'll get power hungry quickly once you get a taste.

 

bosch 044 or a tt pump is fine with 680cc injectors...