i am in the process of installing a HO 5 litre in my 89 f150 but converting to carberated intake. Can I just remove low pressure fuel pump in tank and lengthen pickup or is there a fuel pickup/sender unit from an earlier year that will do same.I am using a mechanical fuel pump.Any help?

 

Just came accross your post, if you are still in doubt about what to do here is what I did.
I have an 88 F-250 with the EFI 460, I left the low pressure pumps in the tank's and removed the high pressure pump that is below the driver's door attached to the inside of the frame rail.
The in tank pumps only deliver 6 to 7 pounds of fuel pressure, I am using a Holley 700 and have had no problems.
Another way to do this is to install a fuel pressure regulator in the return line, the only problem with doing it this way is that it makes the fuel pumps work harder, and will shorten thier service life some what, either way it is a lot easier than removing the fuel tank and modifing the pickup.