What's the differance between the 2 blocks does anyone know ?

The height of the profile on the lock itself.

If you need a set Steve at Alternative Autos used to supply 20v turbo and N/A locks.

Are we talking blocks, locks or a load of blocklocks

If we're talking blocks, the obvious one is the 20vt has an oil feed tapping for the turbo.

Do you have access to the tech data in the workshop manual link?

Note to self, read OP twice before answering!

Yes oil turbo feed point and a crank case breather port on the rear for the collector.

Yes oil catch tank and breathers would be different.

Crank and cylinder bore is the same, but pistons aren't.

On balance I guess you could use a 20vt block for non-turbo engine but not the other way around.

N/A blocks can be adapted for turbo, the breather system picks up on the sump breather port and the rocker cover to then feed to an external after market collector so all doable.

I'm struggling to find a decent 20vt engine everyone on here wants stupid money. Even though it's a community I'll end up taking my
Own engine out

What's up with the one fitted?

Is the compression ratio difference related to a difference in the blocks as well?

From memory 10.5:1 for N/A, 8:1 for turbo.

No the compression is high for a turbo at around 9.2 or 9.8 on the 20vt

According to the Fiat manual the 20vt compression ratio is 8.5:1, 20v n/a 10:1.