I have a 428 Cobra Jet with a dual plane intake and EFI. My first attempt at EFI on the car was a nightmare as the Powerjection 3 I had was a total turd, the longest drive I ever made was 15 miles away from home and it was a nail biter the entire way and I barely made it home lol. While battling the PJ3 I learned a few things
1. the only way to build a fuel system is a true proper return fuel system with a return line.
2. Put a relay on the fuel pump don't let the EFI unit supply the power to the pump
3. Put a relay on the the EFI so it gets plenty of juice, especially at cranking
4. Most importantly provide a clean tach signal (use an MSD ignition box)
I then read about FiTech and how cheap they were and the reviews on Summit's site were overwhelmingly excellent so I purchased the power adder unit because it has the ability to adjust idle for Air conditioning. Since I was previously EFI'ed the install was very quick and simple (1hr) and the car started and ran very well. My Spectra tank pump did begin to make a lot of noise and I had to replace the pump fairly quickly, during this I believe my tank wasn't vented well enough as when I'd pop open the gas cap there would be a large sucking sound and this may have helped kill the pump.
After swapping in the AEM pump its whisper quiet and I've drive the car more and for longer distances than I ever have before. It even pushed me to add cruise control, overdrive, modern stereo, and gave me the opportunity to find out my AC has a problem freezing up. That was something I never noticed because I wouldn't drive the car long enough to encounter the problem lol.
I also have a 37 Ford running a 351C 4v and have adapted a Fox Mustang style EFI Multiport setup and a Megasquirt/Microsquirt computer to run it all. Its night and day difference how the system performs but it also costs a lot more. I think the thing you need to weigh out is exactly what you're looking for and what are you looking to spend, if you really want OEM type reliability its hard not to suggest getting Fox mustang system for your small block car.
I've been lurking on EFI threads in case I ever decide to go with it on my Mach 1. Sure, it's somewhat expensive, but by the time you buy a really nice, tuneable carburetor, like a Quick Fuel, with fuel lines, spacer, gaskets, and tuning kit, you're in over a $1,000.
Look for the posts from Kelly_H. She recently replaced the aging EFI on her Mustang and shared much detail about her experience. She's a very good writer and I learned a lot from her. (I've had the privilege of meeting her and she's also way-cool.) If she doesn't chime in here, I don't think she would mind if you dropped her a PM for specific questions.