My car originally began with the 4age as well. I believe it gained about 80 lbs with the conversion to 4agze. I weighed the 4age and the 4agze and documented what was included in the weight. I agree that the statements online are dubious, which is why I mentioned that I did not know how the 1mzfe's I had read about were measured. When I remove the V6 engine I will weigh it the same way and then I will know. If you go to my website you will see all this information. I have just purchased a wrecked Solara with the 1mzfe engine and manual transmission. Once it is shipped to my house and I begin the work, the original poster will see what is required and how well it fits in the engine bay of an AE92. I believe I am still on topic, since he wanted to know whether it was possible. I've done some searching and I believe if I succeed in my swap, I will have the only V6 powered AE92 Corolla in the US. I have seen other corollas online with V6 engines, but none of them were what the original poster was looking for. Of course, I don't know what possible engine combinations are possible in Australia either. Just thought I would offer him my website so he can see what I've considered so far.
The answer as far as the block goes, I can tell him for certain that the V6 will not bolt directly to the motor mounts in the AE92. The transmission mounts might fit, but I don't think any of the others will, at least not with the 1mzfe. I know nothing about a 3vz engine. I did not consider it because it is also an iron block and it is an older engine. I was looking for something newer.
Good luck and if you do this swap, make sure to post about it, Rur.