I'm sure you read this but from what I've seen and heard it appears to been a one off for the Previa.

Why and how did Toyota build the radically designed Previa in the first place? - Alt Car news

The Toyota Previa is a marvel of engineering with 158 cubic feet of space and a mid-ship slant engine design. Why and how did Toyota build the Previa?

tiremeetsroad.com

 

Thanks, i have read SO much in the last couple of months on the 2tz-fze and -fe, it is still settling into coherence.

That is the article that claims it is a ground up new design. But i definitely recall a mention of it being based on a truck(maybe they meant "van" buy truck tho, regional language can be a quirky thing)

I may have to go and re read it all, - the upside of that being it will aide coherence (i would hope)

 

It's a 2rz , modified to lay flatish. Marketing aside, I have used pistons and rods sold for the 2rz. The crank will swap. It's a2rz same bore centers, deck height. The only things that are different between the two are for the packaging in the previa.
That's not to say it's direct swap the block has oil drains that are necessary on the 2tz to be flat. The 2rz would require external plumbing and a custom oil pan(like a dry sump). And would have to use the 2tz manifolds.

 

So its a HIAce van/UV engine, according to Wikipedia. The more recent 3RZ was the truck branch of the family tree

 

=) thanks!!

That was the info i was after.