I think many of these emission rules are now almost irrelevant.

AFAIK, the RMS (RTA) now look these rules as just being either pre-73 (no ADR27) or pre-1986 (pre-unleaded).

When you look at todays emission laws, Euro 4, Euro 5 etc. the difference between ADR27, 27a or 27b, becomes almost meaningless. Especially when you consider how many of these cars are still on the road, as a proportion of the total fleet.

I am currently going thru this stuff with a few certifying engineers, to get a handle on it. But even on the subject of chassis stampings, I don't think that the authorities are as draconian is you think they are.

Dr Terry