Here's a quote from a guy at LS1tech:
" http://www.summitracing.com/parts/CRT-P4070/
^ I would use this pump right here for a 400hp 5.3. It will have enough pressure but won't need a regulator and its rotary design is nice and quiet."
I think I might just go with this one and call it good. I've got PLENTY of other things to worry about, so cheap and easy is good. It's a Carter P4070
" http://www.summitracing.com/parts/CRT-P4070/
^ I would use this pump right here for a 400hp 5.3. It will have enough pressure but won't need a regulator and its rotary design is nice and quiet."
I think I might just go with this one and call it good. I've got PLENTY of other things to worry about, so cheap and easy is good. It's a Carter P4070