Took me forever to find my engine number and when I did it is extremely faintly stamped on (apparently the norm on mx5 engines). Anyway even after cleaning it up with a wire brush you can only read a few digits of it which correspond correctly with the engine number on the doner v5. Is this going to be a problem on my IVA?

I scrubbed mine with some degreaser then took a photo of it, the flash actually made it contrast much better. It is ridiculously faint though, they must have stamped them on with a bunch of flowers rather than a hammer.

I would hope the inspector has some common sense and realises it's highly unlikely for a replacement engine to have the same digits. Especially if it's the last few digits that are visible.

I used electrolysis on mine to bring it up successfully.