That's not helpful as that isn't how the RAF buy or operate aircraft, as I'm sure you realise
The RAF would buy the avenger second hand when it was worn out. Fit the Volvo 850 engine and instrument cluster from the mondeo but then realise the new additions wouldn't fit. The engine would need an electronic control unit and the speedo etc would be electronic and not controlled by a cable. They would then leave it for a while to avoid embarrassing the senior officers to decided on the new equipment fit. Then the RAF would decide to retrofit the old equipment so this would allow the avenger to become operational. It may have only paid to buy the car, paid to modify it and then pay again to retrofit the original equipment but the government of the day may be able to announce the now old but working cars a second time as a new buy
It's always worth bearing in mind this old but true statement regarding the RAF:
If the the RAF wanted a dog they would buy a cat and then operate on it.