The air injection system is just an air pump, a valve and a manifold on the six, there may be a gulp valve but its not clear because half the system is missing on mine. It is a UK thing as well as export and few were exported to the US in any case.
I am not going to reinstall it but I am still trying to work out from the parts manual if there are any other differences, it looks like the comp ration is lower but not sure why, its only 7.8 to 1 to start with which ain't exactly high. If there are simple upgrades while rebuilding that will improve economy/power I may as well do them.
The problem seems to be that there are at least three capacities of this engine and at least two versions in the Landy, all of which have slight differences between them and make parts non intercghangeable.
What I am trying to do just now is get to the bottom of the seized issue although I would have to say that so far the engine is in much better condition than I was expecting. Once I know what is wrong I will start gathering bits while I complete the axle and chassis build up ready for the engine but since it will take some time to find parts I am just getting a head start.
The problem seems to be that rarity makes finding out about them not so easy
plus it has to be the largest and heaviest engine I have ever rebuilt, all the ones t I have done in the past have been various motorcycles, MGB's, MG Midgets and 70's Ford Crossflow engines which are all significantly lighter and more compact.
Plus I was a lot younger when I did most of these......