When I was at Holley we were developing a gerotor fuel pump that ended up being marketed as the Volumax. They had IIRC a 170 GPH iteration and a 250 GPH version. The 250 had a bigger pump section and a stronger motor. At first they both shared a common external body with a single 1/2" inlet and outlet. The 170 performed perfectly well in the lab, but the 250 had a significant cavitation problem. The outlet would develop a bunch of entrained air and made a lot of noise with a big drop in flow. Eventually the guy doing the design and testing decided to add an additional 1/2 inch inlet opening (now we had two inlets and a single outlet.). The air disappeared, the noise went away, and the outlet volume cruised right past the 250 GPH target with no distress. The inlet side of a pump is pretty damn important...
I agree 100% on the effects of inlet restriction,this was also discussed over on Bill's test rig thread it is incredible how air can find a path given enough pressure differential,kind of like a mouse crawling under a door.Running the larger diameter tube 427 type pickup may not solve these issues but it surely can't hurt.Ford chose to use the larger tube pickups on their performance engines such as the 427,Boss 302,429 Boss and CJ/SCJ's,in the case of the 429's they even developed a dual entry pump though I think that had more to do with rotor pulsing causing spark scatter but it may be related.As far as the funnel or bell shaped pickup while I've seen no comparison to prove it,it sure looks like should work better.