Hi David,
$4500 is a big wad of cash for a mod that potentially might not add that much HP. Your money would be probably better spent on some good head work a cam and a re-mapped ECU.
There are some guys arround the country developing these motors now and they have been getting some good results.
Chipmaster in WA have been getting some surprising results from tuning an unopened motor. Check out the development they have been doing on their
Monaro test bed. It's making more rear wheel HP as a GTS300. All they have done to it is 4-1 extractors, a cold air box and done a heap of dyno tuning of the standard ECU. It now makes 247KW at the rear wheels where a standard GTS300 makes 225KW on the same dyno. The car has run a 12.98 quater on standard wheels and tyres and standard auto trans/converter. All the tuning and mods only seem to have improved low end HP rather than make for a peaky engine.
The Ute they have been working on has head and cam work as well and makes 274KW at the rear wheels. That equates to 367HP at the back wheels. From memory the most powerful Cobra that got on the dyno at DVSF2 only made about 350RWHP.
I think that'll be more than enough to scare the hell out of me.
This is the route I'm planning on going initially. Garrett has got me thinking about superchargers though.
Cheers