Are they exactly the same and perfectly interchangable or do they have different PCDs, bore, etc or different wheel width or something? ie could i stick jap 300zx std wheels on my uk model?

Jspec has the same wheel all round which take the 225/50 R16 tyre. They're 7.5" rims with a 45mm offset.

 

The UK has the above as front tyres and wider wheels at the rear which take 245/45 R16. They're 8.5" rims with a 35mm offset.

 

If you look down the side of the car, J wheels (and UK front) look flat and UK rear look dished inwards.

 

So, don't fit Jspec rims at the back of yours as it won't look as good.

Jspec has the same wheel all round which take the 225/50 R16 tyre. They're 7.5" rims with a 45mm offset.

 

The UK has the above as front tyres and wider wheels at the rear which take 245/45 R16. They're 8.5" rims with a 35mm offset.

 

If you look down the side of the car, J wheels (and UK front) look flat and UK rear look dished inwards.

 

So, don't fit Jspec rims at the back of yours as it won't look as good.

 

 

Just swapped my j specs for uk and the uk wheels look shit loads better on the rear, they fill out the arches more

Exactly. Gives a much more aggressive stance. If I was to retain the original rims, I would have sourced UK rear wheels.