Fitting a New AC Weller Engine is in my view the correct approach, but i would say that as i make them! but it does survive the the originality of the car albeit not the actual original engine, we are getting 140-150 BHP now & in fast road form has a very flat torque curve.
Several of my engine perform well in Historic Racing & shortly one will be fitted in a Racing Ace.
Values of Weller engine cars will in my view increase to that of the Bristol version, but in the end it is what the owner can justify spending, it would be a shame to fit a Ford 2.6 if it was not fitted originally, they are becoming difficult to find now, but they are good engines!
By the way the Weller engine design is 100 years old this year, but was very advanced for the period!
Robin