Cranks but will not start

Ford e350 7.5L V8 460 MFI RWD 27’ Class C Motorhome.

I replaced the fuel pump and the pump regulator (because there was gas in the vacuum line going to the manifold).
Put in new plugs, and a couple of the wires, that was incredibly difficult!
Replaced the battery, and cleaned the MAP sensor.
It acts like the timing is off, reset it. But nothing.
I can turn the distributor while cranking but it doesn't change the way it’s cranking.
I checked the firing order, thought maybe it was off, looked up online according to the vin (eighth digit “G”) but it did nothing so I put it back the way it was and for a brief second it started but it shut off immediately.
It cranks and cranks, and every once in a while it acts like it’s going to hit but doesn’t.
Now it’s acting like it doesn’t have enough juice to even crank, and it’s got a good battery.
Could it be the starter or might it need a bigger battery?
And funny thing, the generator is acting the same way!
What am I missing here?
I’ve got to get it moving again. I had it running a week ago and took it for a drive, I got two blocks away from my house and it coughed and sputtered and shut off. Now it’s sitting in a parking lot and I’m afraid it will get towed.
Any thoughts or suggestions would be very much appreciated.