there is plenty of anecdotal evidence to suggest that the intercooled ones do much higher mileage before cracking heads. I have now seen 5 that have done 500,000kms without doing the head. However, there are also a number of Prados around(same intercooled 1KZ motor) that HAVE cracked their heads, so it can be a bit of a lottery. What i will say, is that the intercooler lowers the EGTs by quite a lot when under full power. I'd also speculate that nearly every single intercooled 1kz that cracked a head, did NOT have an aftermarket down pipe, and exhaust.
From the 185s that i have seen (and owned a RZN185) rust hasn't been a big factor in the 185 series Surfs at all yet, but (by logical extension) can suffer in the usual places if used a lot on beaches or used to launch boats. A thorough pre purchase inspection is invaluable. Make sure you have a look at the roof rails, or roof rack if it has one(specifically the mounts/bases) as they can provide an entry/starting point for rust( you will see paint starting to bubble if there is an issue.) this is generally a cheap and long term fix though.
also check to see if the load security d shackles in the rear luggage compartment are rusty- this often means that the truck has been used by sea divers, snorkellers, or fishermen, and the wetsuits/waders have been chucked in the back.
The intercooled one have held up in value(plenty for sale at around $11-14K still), so if they intend to do a lot of towing, just make sure they look at other options for similar money(think landcruiser and patrol/safari).
Ergonomically they are real practical and easy to live with. The back seats fold up/down to make a flat sleeping/storage area, tall enough for big fellas even. IMO the best sleeping platform 4wd wagon.
There is plenty of ideas on this forum,( and others) to seriously help delay any head cracking.
read here.
viewtopic.php?f=22&t=43160&p=439349&hilit=+1kz#p439349and here
http://www.toyotasurf.asn.au/forum/view ... hp?t=20880
and a guy in Palmy has a jig, so can supply bolt on dump pipe and exhaust system for KZN185s (3" diameter).
you also want to contact forum member "Zed", he knows lots about lots, including lots about the 1KZ.