Hi, I just pulled a 5.0 out of my '59 custom sedan because I could never get better than 8 mpg with it. The original 292" V8 with three burned valves got 15 mpg highway. This is a daily driver, not a trailer queen.
It's definitely a 5.0, the crank is missing some counterbalance lobes compared to a 302, it came with flat belt accesories and a fuel injection intake and mustang exhaust manifolds and catalytic converters. The plugs were long reach that only fit a '95 mustang, according to my auto supply. But I could never get it to run with a HO firing order, it would only run on 1-5-4-2-6-3-7-8. It came with the computer plug chopped off the harness, so I hooked it up with a weind 4bbl intake, a holley 450 CFM 4 bbl, and used the smallest jets I could buy, 51. It wouldn't start cold with a '64 mustang ignitiion, and a hotter coil just shorted out across the distributor cap in wet weather, so I ended up with an '81 granada 4.2 L ignition that has a rectangular frame coil and a big distributor cap that takes the high voltage without shorting. The compression was okay, 120 to 150 psi, and the vacuum was pulling 20 in. steady idle, but only 10-18 in. at 55 mph in flattish country. The centrifugal advance was working in the distributor, and so was the vacuum advance.
I wonder if it had the wrong cam? Was this a failed repair, with the wrong cam installed, or was it just that the '95 Mustang cam has so much overlap for the fuel injection that it won't pull a heavy car (4100 lb) like this with a carburator? I had a 3.56 ratio rear axle and 205-78-14" tires (same as the 292 V8), so it should have been geared low enough. Is there a pickup or van version of the 5.0 engine that has more of a torque cam? Can I put a '77 302 pickup cam in it, or is the 5.0 cam mechanically different? I don't have a lot of money, I'm retired, I'm just trying to decide whether to scrap the 5.0 or put it in my '76 F150 instead of the 11mpg 360 V8 with the cracked block. I put the '81 4.2 liter V-8 back in the '59, I pulled it out for low power but the problem turned out to be the gas tank outlet was plugged up with dirt. The new '59 gas tank is not compatible with a rotary electric fuel pump even if I could find a 5.0 fuel injection harness and computer cheaply.

not that anybody cares, I guess, but the '59 Ford sedan got 17 mpg yesterday on a 4.2L '81 model long block with the same carb and intake and transmission and rear end as the '95 5.0 long block at 6-8 mpg and repeated stalling. The cam chain was not slipped on the 5.0. It got where it just wouldn't suck the carburator at suburban speeds, a Holly 450 CFM 4bbl on a Weind manifold. Unless there is something weird about the cam in this particular 5.0 block, I am forced to conclude that 5.0's need a custom non-overlap cam if you are going to use a carburator on them on the street. I'm running a '64 points distributor now on the 4.2 L, I don't need the high energy of the '84 distributor with a fancy electronic module to start the '95 5.0 heads in the winter. I don't like the fancy electronics, it took me a month to prove that the stalling 5.0 didn't have an electronic problem, by first replacing everything, then proving that the spark was still working after the stall by using an AC current meter (for electric motors) on the coil wire. Part of the economy problem of the 5.0 may have been an '84 distributor (no-centrifugal-advance) with, as I bought the 4.2L , a '79 ignition module. It's possible the '79 module did not have centrifugal advance and the '84 module it should have had did. It's pity, but even if I could buy a '95 wire harness and computer, (I haven't run across one in 3 years I've had the 5.0) the 5.0 injector iintake manifold won't fit under the '59 hood without a ticket catching hood scoop.