GPM Fuel Pump for 427 FE

[E5USMC]

Just curious what GPH mechanical fuel pump a 500+HP 427 FE would require. I'm currently using Carter 6905 ( 120 GPH) pump on my 427/482 engine and I've notice under hard acceleration it can sometimes die / stumble that feels like fuel starvation. The other day while on the interstate I hade a long run to get around a handful of semi trucks and even though only around 3-3.5k rpm for that extended run it started to try and die out. When I kick on the electric pumps, it clears right up. As long as the electric pumps are on it never dies or stumbles even when under hard acceleration.

I've read good things about the Carter pump so I'm curious if maybe my mechanical pump is having issues or if I might need a higher GPH pump.

Thanks for the advice.
AKM