The plan wouldn't work
The precision required by Doc's hare-brained plan makes it impossible to execute with the DeLorean's non-digital and inaccurate speedometer and the clock that doesn't -even- have a second hand. (I know it has a first hand, and a second hand, but I mean the time unit measurement, not the 'between first and third)
You don't have enough precision for timing a lightning strike (even though the movie's version was a very slow lightning compared to real ones) well enough that it would strike the hook just when it's touching the wire.
Let's do some math.
The DeLorean will move almost 20 meters (19.7, rounded from 19.66972222) in HALF a second.
Think about it - you need the car to move exactly 88 miles per hour (we can of course say it's enough if it moves -at-least- that fast), which means, it will travel around 40 meters every single second.
If you are wrong by HALF a second, the car will be 20 meters in the wrong direction (either passed before the lightning hit, or hasn't reached it yet).
There's also no 'leeway', so that the car can touch the wire for more than half a second (because it's moving so fast, it'd be 20 meters away in that time), the hook doesn't 'stretch'..
So you can't err even 0.5 seconds. Or 0.25 seconds (which would mean the car is 10 meters away from the wire).
There's NO WAY you can time it that accurately with that clock. The only reason the plan worked, is because they had the best luck of anyone in the Universe.
Or, hrm.. a bad writer on their side. Take your pick..
By the way, even -if- you had the perfect calculations and the clock did have not only a second hand (which wouldn't be enough for this precision anyway), accelerating a car that requires you to change gears (though why would a DeLorean require that, I don't know) and starts much later than calculated (I didn't even mention the horribly inaccurate alarm clock of the fifties - there's -no-way- you can set an alarm with sub-second accuracy with that thing!) - it's such a wildly fluctuating process, that even if they tested this 88 times, there's no WAY they can trust to reach that kind of accuracy every time.
Besides, I am sure they wouldn't have had time (how ironic!) to test it 88 times..
That plan would -never- have worked in real life. I would like for someone with an actual DeLorean to test this sort of thing, and try to time it perfectly, and see how well they do.
Maybe if you try it 88 000 times, you might by luck get it 'perfect' once. But Marty and Doc only had -one- shot. I think this bit requires the most suspension of disbelief (even as a kid, I wondered about that).
The car can't even be 5 meters away from the cable when the lightning hits. That would be 0.125 seconds of time, by the way. Good luck timing it that way with 1950s equipment.