12psi is fine, unless you have a boost leak it would still be within the turbos efficiency window. After 14 to 15 psi the turbo pushes more hot air than anything and it's well beyond the capacity for most intercoolers to make up for. If you had a boost leak you could have easily over worked the turbo.
From what I've seen even 1JZ's advertised as rebuilt that sell for around $1K are often in sad shape... Used is still, afterall, used.
I really don't think you understand entirely what's involved in the swap or have an unrealistic view of the entire scenario. I've yet to read reports from someone who said it was cake and went without a hitch and only took three days as planned. It's your car though, so have at it. You'll find there is a section over at
www.supramania.com specifically for MKIII swaps such as the 1JZ, 2JZ and 1UZ where you'll find a great deal of information and advice. You should check it out.
Good luck!
Green, just from skimming it, that site's a little dated... as a community we've learned much since. Much like the SOGI site, it's a good reference for some basic info, but isn't a good source of current and up to date information. The details about 16psi warping the head is garbage, N/A cams have been proven to cause an overall power LOSS, they are NOT a good high-rev engine (tend to grenade much past 8000RPM unless destroked, from what I've read). There are MUCH better, up to date references online if you look around.