I spent most of my summer chasing the same issue in my 440.
It ended up being the fuel pump push rod. When I removed mine and compared it to a new hardened one from Hughes Engines my old one was about 1/3" shorter.
The cam had also worn it to the profile of the lobe.
I built my motor in 2010 and used the original pump rod and a Lunati Voodoo cam. Maybe 1000 miles on it.
I just got it back together this weekend. Took it out today and all is well. She runs great.
Like you, with hoses on the pump and straignt to a gas can, it would not pump at all before I changed it out.
Good luck