It would depend on the size of your injectors and the fuel pressure you are running.
If you have stock injectors and fuel pressure regulator then one pump is all you need.
The in-tank 1990+ pumps put out about 100 PSI against a blocked head.
They are rated at 125 LPH (33 GPH) @ 310 KPA (45 PSI) so the stock pumps can put out more than enough fuel for the 460.
A 460, 351 & 302 have a top fuel pressure of 45 PSI (310 KPA) and a 300 engine 60 PSI (415 KPA) so there is no problem. If you want more than you would have to go with an adjustable fuel pressure regulator.
The Injectors Flow #/HR are for the 300 = 14#/HR, 302 & 351 = 19#HR and the 460 at 24#HR.
So the injectors @42 PSI for the 14#HR = 2.45 GPH, 19#HR = 3.3 GPH & 24#HR = 4.2 GPH.
So a 460 at WOT = 33.6 GPH @ 42 PSI. and that would be enough fuel with a 33 GPH @ 45 PSI as the pump would put out more GPH at 42 PSI.
Any engine under the 460 would have more than enough fuel.