Having built 4 7M's, and two of them being very rare stroker 7M's, the idea of using off the shelf parts from GM that make seriously insane power under forced induction is very tempting indeed.
Think of this.
The alloy block LS7 is lighter than the 7MGTE engine.
It is shorter. (It has the weight set back more for better distribution.)
It is not as tall. (Hood height is no issue.)
It is wide, but not much wider, so exhaust manifold clearance is not an issue.
The oil system is better.
There are TONS of aftermarket parts for these motors. (Heck, you can get every part for the motor, including the block aftermarket if you want.)
Now for the reality check. Displacement ability. Stroked the 7M will get you 3.2 or 3.4L at the most. There are 7.0L stock LS7's out there, and slightly more if you want it. (Why would you need more than 7.0L of displacement, especially under pressure... ?)
Because the MK3 has a long engine bay, when the V8 motor is installed, you have all this room between the core support and engine to place the turbo's and your radiator and intercooler.
I'd have to imagine that a mild 10:1 LS7 engine of 7.0L displacment with 10 lbs of boost ontop of it would make insane amounts of power, and be very close to stock weight as well.
There are 6 speed transmissions out there in F-bodies around the globe.
Aftermarket stand alone ECU's and wire harnesses too made just for this engine. Coil upgrades, dampers, pully's and all kinds of cool stuff.
So, when you see a MK3 with dual 3" exhausts that sounds like a turbo charged sprint car... look out, that would be the ultimate MK3 chassis/engine combo.