The 3SGE is meant to be robust, to say the least. I wouldnt say no to turbo or S/C it. Look at the Toms 280T.
It was just back from getting a new ECU and Map recently, along with a new fuel rail to cope with the uprated pump.
In retrospect I would say lower the compression with steel rods, L/C pistons and thicker gasket. Then when the Turbo kicks in at least you can run reasonable boost. However, Low boost IS better than No boost!
As far As a 3SGTE bottom end, not sure how that would work. I would have thought that the engine mounts would have been on the wrong way as the Altezzas engine, as you rightly pointed out, is the wrong way round [Not an easy fix]. The bottom end is also different the 3SGTE already has the forementioed set up for the turbo application [ Bonus] but I believe the sump requires modification to fit [again not an easy fix]. So I think ill try the solder idea first.
What about a 2JZ-GE? from the is300 that sits the same way as th supra GTE does it not? If that fits in the same chassis as the altezza would this not be a option? engine running gear and aux'.
Tezzaman. you would be in tears? You big girls blouse! Its only a car it will live again, Hopefully :D