Though I haven't read much into the JZ engines, I'd throw in whatever little I know about them,
A) There are a few differences in the earlier and later 1JZ engines, The very obvious one you mention is the addition of VVTi in the later ones, Other than that another major difference is that the earlier generation 1JZ's were Twin Turbo'ed from the factory while the later ones come with a less complicated and easy to work with single turbo setup,
Not sure about the block layout but the head design was obviously changed in both gens, The VVTi ones apparently cured some faulty valve design problem that was present in the first gens that caused the turbos to wear out prematurely or something, (You should wait for some one with hand on experience to enlighten you on this problem or probably do some googling around)
Apart from that the HP on both gens remained the same around 280 but the torque was increased in the later gens by a bit.
B) They come rated with around 280 HP from the factory and something above or around 350 NM of torque as far as I remember,
They will run on normal petrol with some timing adjustments but to get the desired performance out of them and for smooth running you should at least run a good ratio mixture of high octane and normal gas, (I suppose this would be a trial and error thing)
C) Your location is listed as Karachi, So you'll probably be better off getting in touch with the car geeks there to guide you to a good shop, There are lots of them on here that could guide you the right way,
I believe Sher Shah is the place in the Karachi? Go there in your free time and window shop for a while you'll get an idea of what you want and are looking for.
D) Normally a dealer who sells you the engine would give you some sort of running warranty, i-e, The engine will start right, The wiring and other stuff that he provided should work right, The engine itself should be in good nick and don't smoke or burn too much oil,
If any of those things or other provided "warrantied" things go wrong he should replace them for you including the whole engine itself,
(I believe this is the case in every city but ask around just to be sure)
E) I think most of the engines available here come with a 4 Speed Auto transmission and I have yet to see one here with factory manual one,
F) People with hands on experience with crowns and engine swaps should be able to help you here,
G) Well about a month ago I was actually out with a friend who was looking for the 1JZ-GTE motor for a side project and the prices we got here were between 70 to 85K with all the bolt on with the motor like the ac,PS pump etc, Auto gear box and all the wiring and ecu, A complete package to sum it up,
Do Note:That prices of both the first gens and the later ones were pretty much the same, So if you are going to do the swap I'd say go with the later ones, Because of the single turbo less complicated setup and less problems with the new head and most importantly a newer motor with lesser miles and less abuse,
Also seeing that you would be swapping this into a crown a great platform to begin with, I'd suggest you look around for other options too,
Like if you really don't want a high powered turbo setup and want something with decent pull and less problems then do consider the 1UZ-FE or the 1JZ-GE or even the 2JZ-GE if you manage to find one, They have less stuff bolted to them and hopefully they'll have much less to go wrong and be more reliable and easy to live with on day to day basis.
I am sure you've done your research but just attaching the pictures for the info and for reference
The 1st Gens 1JZ engine in a Toyota Soarer
The Second Gen VVTi 1JZ-GTE,You can sort of see the single turbo layout,
Wishing you good luck with your project,
