I think you’re on the wrong track to solve your no start problem. Mindless part swapping is a big NO on the Jaguar V12. It will empty your pocket in very short order and will unlikely produce the results you expected.
Have you priced a new Marelli amplifier?
Please take this as a useful suggestion/reminder, not as a troll-like comment. DO use of the magnifying glass in the upper right corner of the screen. This is the search button.
This thread on the topic of Marelli amplifier was active just last week:
To sum up - the Marelli V12 is essentially two I-6s with a common crankshaft. Operates as such. The engine will start and idle on one bank only.
If your coils are connected correctly (you indicate there is fuel and spark in post #1), I can’t think of another reason (besides my concerns about the replacement harness) the engine won’t start.