Engine swap and classic insurance, mot /tax exempt

So I was reading about tax exemption and MOT stuff , vehicles of historic interest etc and something caught my eye,

Engine replacement if the same cc etc,
And the part about engines that were fitted to the model before it ceased production

The thing is having classic insurance would that be adversely affected, or would the mot tax exemption be changed?
I have an 85 reg 110, ex military 2.5 n/a and was wondering.

What stated regarding MOT exemption and substantial change seem perfectly clear.
Engine.
Alternative cubic capacities of the same basic engine and alternative original equipment engines are not considered to be a substantial change.
If the number of cylinders in an engine is different from the original it’s likely to be, but not necessarily, the case that the current engine is not alternative original equipment.”

I don’t know why you believe classic insurance is affected, insurance is individual, with premium based on the vehicle and driver.

It was more that would an engine swap mean it wasn't an original vehicle anymore. 8)

Alternative cubic capacities of the same basic engine and alternative original equipment engines are not considered to be a substantial change.
If the number of cylinders in an engine is different from the original it’s likely to be, but not necessarily, the case that the current engine is not alternative original equipment

1. Any alternative original LR engine if similar, even if has a larger CC. Is okay.
2. Increase in number of cylinders is not okay, (example no V6 or V8s if the original was a 4 cylinder)... unless there is no alternative original equipment engine available. So a loophole, now if a similar original isn’t now available then fit whats available within reason, but then the chassis and suspension being changed is a no no.

So a 300tdi would probably be okay by the look of it,

As I read the regs, if your non standard engine swap was done 30 or more years ago your fine, eg a v8 into a series landy in 1980 .