used the ford system
I don't have experience with the "new Holley EFI" systems but we put a pro-jection throttle body system on my dad's 71 f100 360 and it never ran right for a year and a half. We pulled it off and are going back to carb.
I converted to 88 ford EFI system (speed density) and was very pleased with drivability, cold starts etc. My setup came out of a cop car and was low on power compared to my 289. I converted to Mass air and currently have an intake, heads, throttle body,bigger mas air meter and soon a cam and roller rockers. The 88 crown vics are rated at less than 200 hp. My fuel economy went from 11-12 city / 17-18 hwy to 16-17 city and 22-23 hwy. I think it will do better with new oxygen sensors. I'd go with a mass air setup (found on mustangs) with the upper intake flipped like a crown vic, this is essentially what I have now. By rotating the upper intake the throttle cable is very simple to route and hook up.
My 289 had performer cam, hooker comp headers, dual plane intake, pertronix and edelbrock 600 carb. I dropped the stock crown vic motor in wtih a new oil pump, new paint and the old headers. I think the reason it felt down on power is the restrictive 49mm throttle body and grannie cam.
Having experience with both systems, I wouldn't recommend the holley pro-jection to anyone. The ford sytem can seems a little intimidating, but is far superior.
Look at all the companies that make performance parts for the ford factory efi systems and then how many make parts for the projections systems. FYI the holley projection systems use late 80's chevy caprice and half ton truck parts with a holley computer. If you're dead set on throttle body injection pull the parts from an 89 caprice donor. After all our experience with the pro-jection stuff we just wanted the truck to run again without more hassles.
Bottom line, you will be much happier with the drivability, cold starting, responsiveness, power potential and fuel economy with the ford factory system, that's why it's so much more common than the holley systems.