You don't mention which generation model you're wanting to match FD - GD - PD
i30's are called Elantra GT in the US and many parts match (though not all), also most Aussie versions are locally tuned so generally best to stick with items that are listed directly for your vehicle unless you definitely know a certain part will match.
Aside from local tuning Engine size/type differences will alter suspension setups as well so best to stick with correct model products, as far as seats are concerned are you meaning from same generation swap or maybe PD seats into GD
if same generation then bolt patterns will match but if swapping generation you would have to take your own measurements and also check if electrics are plug and play.