Gollum, are you secretly me?
For about 3 years now I've been planning a twin VFR-engined, twin supercharged Mini, with a curb weight around 1000lbs and packing at least 600hp. Ever since I was on the Formula SAE team at college, I've wanted to build a car of my own that would perform in the same way, but with the ability to blast around on public roads. There is just nothing like being able to turn as hard & as fast as you can at 60mph without even so much as tire squeal.
Remember that the VFR800 powerplant is actually 90º -- it's the RC45 that has a 180º crank. Unless you make a custom crank for this engine, you won't get it to sound like a Ferrari.
As far as power is concerned, I don't advertise this, but I've seen 167hp at the wheel on my supercharged setup -- that's right around 190hp at the crank. There's no doubt in my mind that the stock internals can handle 200+hp. With the Mini project, I was planning on running forged pistons & rods, and also adding an intercooler, and then 300hp per engine should be cake with pump gas.
BTW, I love the LS1s as well, and plan on doing the E36 M3 swap in the next few years.
Good luck with your project.