Gary,
As regards the steering, I can only quote from the government website describing the 2018 rules
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/670431/vehicles-of-historical-interest-substantial-change-guidance.pdfso I make the assumption that if it is the same type of steering gear, then it would pass the that criterion.
"Axles and running gear – alteration of the type and or method of suspension or steering constitutes a substantial change;"
I note that you previously said "Now at present it has 4 points for original axles and suspension..." so do not understand the problem
I also don't believe that if it is not declared as a VHI it has to have a Q plate. The VHI is a voluntary declaration to gain the dubious benefit of not requiring an MOT test, with the possible outcome that restrictions on their use may be imposed at some later date. If the vehicle currently has a V5 and was being used by the former keeper then surely there is no need for it to be examined for originality?
We obviously differ in the way we view this car, and that is fine because there is room in our club for all types of folk.
I see this as an opportunity to restore a very rare car to its original form, for the cost of an engine rebuild. If more power is wanted, then it would cost no more to extract 100bhp during the rebuild as it is likely to need pistons, liners, crank, rods and cam etc. anyway. So approx. 50% more power for free, with a lighter engine than the Jaguar unit.
Good luck with your bidding. Graham.