Look around the cylinder head bolt holes to see if there are any prounounced ridges from having the wrong studs, any heavy scratches on the sealing surface that does not look like it would clear out. Look for cracking.
Check cam journals for scoring, combustion chamber damage, flatness. You can mill the jz head quite a bit. Mine was so warped that you could set it on the ground and it could tip back and forth and the machine shop just milled it and it's all good. Look for bent valves as unlikely as they are you never know. Make sure the spark plug threads aren't damaged. Check for matching cam caps because they are not interchangeable.
Also be aware that the older ARP head studs came with small washers that would gouge into the head. This can be repaired by a competent machine shop, but it is something else that you have to deal with.