What do I need to look for in my next Supra?

[finaltable]

As stated in another thread I am looking for my next Supra. My first was a '90 NA Targa. Most of these have well in excess of 100K miles (I know this is not a bad thing; mine had 150K on it and still ran well when I sold it) so an engine replacement is going to be in order at some point. From what I have read here, it appears that either a 7M (obviously) or 1JZ are pretty straightforward but a 2JZ is not.

While the bodies are almost identical, I don't know the differences in the cars as the Mark III progressed from 86.5 to 92. Since I can't exactly just order up a used Supra I need to know what would be optimal, e.g. 1992, what is okay, e.g. 1990-1992 and what I should avoid, e.g. 86.5. (It is entirely possible that any Mk III would be fine, though I thought I read that it is easier to put a 1JZ into the later ones. I just don't know when "later" starts.)

Also, I am open to getting a NA MkIV. I have never been in a MkIV, much less driven one. I do know that my Mk III is my favorite car I have ever driven, and I have driven something from almost every mfr including Porsche (944) and Ferrari. (Okay, the 308GTS was more fun to drive. It is not a daily driver, though.)

I am a business professional so I am not going to be nickel and dimeing this. If Toyota sold new Supras I could afford to buy one. They don't, however, and nobody else sells a Targa sports coupe, so a used Supra it will have to be. I am fully expecting to buy it off eBay or Autotrader and have to fly someplace to pick it up.

I know generally what to look for in a Supra from having bought my first one. I'd appreciate thoughts from those in the know about specific years.