The problem I see Ben is that very little records are kept when the engine is changed. If you fitted an engine of similar year/type and kept a record of what you had done then a lot of the problems would be reduced. If you ground off and re-stamped the original number and again kept a record I see no problem. If you bought a short engine and fitted, it would not have a number so you would have to transfer your original one. This would be acceptable. It is what Ford and British Leyland did when they rebuilt engines for service and what we in the dealership did when we fitted a new block or engine.
If however you fit a Cargo or 6 cylinder engine then you are changing the tractor build and it no longer is a Historic Vehicle because there was never a 6 cylinder Major designed by Ford sold back in the day. It is something you have made yourself and would possibly be inspected for road worthiness/type if you try and claim Historic Vehicle classification. I do not know.
Tractors like the Doe, County, Roadless, Thomas et.al were all sold as modifications when new and registered as such so there would be no problems there.
I would suspect a Dexta is less of a problem because the Serial Number is not the engine number unlike the Major.
The diesel checking does go on, Rick, it happens at ploughing/working days, County Shows and vintage shows. Dealers and Young Farmers have fallen foul of it and so have contractors cutting verges. People who keep their own horses and use an old tractor to top the fields should also be using white diesel. The reason it is not strongly enforced is the lack of testers but one could be unlucky one day.
Do not get started on the safety cab or frame laws in the Health and Safety at Work Act as applied to our tractors, otherwise we will be here for months if not years.
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