I got a 2.0 from a MX-5 NC which did spin it conrod bearings on the crank.

Is it worth rebuilding/ tuning it or shall I just scrap it and sell the head and a couple of ancillaries for a couple of hundred pound?

i seem to remember the bottom end of these engines being a bit week,small oil cap didnt help either.
check the price of a rod,bearings,pump,gaskets and a grind,prob be best as a doorstop.

Worth taking the caps off and seeing how bad the damage is ?

If its bad and beyond saving split it for bits

But if its only light damage it might be worth saving as there's always a few MX 5 Mk3 owners looking for an engine

Seems to be a few of these that have failed, I read that folks tend to not keep an eye on the dipstick, One of the specialists reckon a weekly check and always have it on MAX on the dipstick...

Yes, I have taken the sump and caps off, you can feel the damage with your finger nail on the crank. On two conrods the bearings don't even fit.

So it would be a full strip and rebuild with a crank and rods.

Don't know who designed that dipstick, but it is worthless to use. As soon if you pull the stick the oil runs via the upstanding edges to the max marking.