I made almost 600 WHP on a single walbro 255, corvette fpr, and a -6 feed..... It'll be fine. You can make over 1000 on a -8.
I run three walbro 255 externals, on E85. Two will take you to around 700ish.
Agree with the Bosch pump statement, I'd probably do that if I didn't get these pumps so cheap.