This is true. The 7M isn't really that great of an engine. I had one sitting there and a Z with out an engine. It's the only reason I did it. They are limited by the head ( power comes from airflow), not bottom end strength.
If 900 rwhp is the goal a 2JZ will have a miserable powerband, 6000+RPM for boost and it's not happening with stock cams (expensive), pistons, or anything less than 110 octane. An LS1 with boost can make about that with good spool and on pump gas. You can make big power out of small motors but they will lack torque, need alot of boost, octane, and rpms to make the boost. Drive an n/a Corvette and an n/a Z with about the same power to weight and ask yourself, which power band you like more.