I must agree that it's a totally different beast. Yes, the SBC will have more torque, and yes HP/ Dollar will be a better thing. However, the driving aspect - you'll never get the experience the flat - 6 offers in terms of revability. A flat 6 at 200HP will outlive a SBC at a comparable power level if driven the way flat 6 can handle it. Keep the revs up on that crate SBC and you'll probably be breaking valvetrain stuff all the time - unless you spend the big bucks on roller, and then it's nasty to drive. That's one of the best things about the 911 is the tossability of the flat 6.
You'll be tearing down every 30K for various reasons. Not so with a flat 6.
If you install a SBC it's also got limited appeal now, so if you ever get bored and toss it, then you're all done. Save the money for a clean 3.0 or 3.2 around 100K and be done with it. You'll easily get 200K out of it if you maintain it - and you'll be able to beat the crap out of the thing, it'll live.
Also, to prove I'm not a Porsche snob - here is this morning's driveway shot - I've got projects booked till 2007 --
