Well, that's not true. That 5-9 number is for carbureted motors, and I would say ideally 5 PSI for those. The stocker TBI pump for SBCs and earlier TBI 454s runs 13 PSI consistently and effectively per the demands of the powerplant when in proper working order. I'm 99% sure my Jimmy is still running the stock pump, and it still gets me from A to B no problem. Granted, I don't know how long it'll keep going, but thirty years and 183,000 miles is quite a haul. If you plan to build a more aggressive 350, 383 stroker, 400, or 454 down the road, then you'd see insufficiency issues. The best way to compensate for that on the fuel pump end is to switch to a 1994-95 TBI 454 stock pump that pushes 30 PSI or go to an aftermarket Walbro pump. You have to do more than that to fully adapt the fuel system, but that's just pertinent to fuel pumps. If you're just running stock or slightly modified, the Delphi replacement pump is generally accepted as the best to go with. RockAuto is likely gonna be the best price you find for that one, and there's a 5% discount code in their preferred vendor section.
