While I sadly don't have a 2.6 Ace, I do have 2 Allard Palm Beaches that use the same Ford Zephyr 2.6 engine and gearbox. Both need restoration and engine rebuilds. As the Zephry was never sold here in the US, I have no idea on parts availability. Is there a source in the UK for engine/gearbox parts?
June and John from Goldendays (http://goldendaysparts.co.uk/ (http://goldendaysparts.co.uk/)) helped me a lot. You should contact them first. They are very kind and helpful.
If you need more power: https://www.chesmanengineering.co.uk/zephyr (https://www.chesmanengineering.co.uk/zephyr)
These guys make a complete re-build for you: https://zodiacmotorservices.com/ (https://zodiacmotorservices.com/)
Maybe these guys have the parts you are looking for: https://newpartsonline.co.uk/ (https://newpartsonline.co.uk/) and https://www.jonniejumble.co.uk/classic_car_parts/vehicle/Zephyr.shtml (https://www.jonniejumble.co.uk/classic_car_parts/vehicle/Zephyr.shtml)
Last but not least a guy from down under with a lot of parts: https://www.yesterford.com/ (https://www.yesterford.com/)
I can highly recommend Chesman motorsport, I was there on Friday picking up a Raymond mays head, they are very knowledgeable.
Thanks guys!