if you think have everything else worked out you may want to read up a little more on GN's then as there is a lot to think about when doing a motor buildup.....
Stage2 was a Buick Motorsports aftermarket offering (from GM dealerships). On center blocks were thought of as stronger and none of the factory GN parts were interchangeable. Off Center blocks could interchange some stock GN parts (crank/intake etc).
The blocks are getting to be as rare as hen's teeth on the used market (nearly nonexistant now) and can no longer be purchased new for a few years now from GM. New virgin blocks command $3500+, forged cranks from $1200-3K, forged rods are fairly easy to find used for around $500, and most major piston manufacturers offer a slug for the motor or can make one $600-1K). So there you have $5K in parts for the shortblock without maching and oil pan/pump provisions (add $2-5K), Next decision is heads.... GN1's or Stage 2 is what most run. $2500-5K+ easy. Next comes intake.... Either rework a stock carb'd Stage 2 intake for EFI or have a custom one made $500-3K. Aftermarket fuel management $2-4K, custom headers $1500-2500...... the list goes on and on. You can pass the $20K mark in a blink of an eye. They can make upwards of 1400hp!
Best way IMO is to buy a complete longblock or complete running used motor from someone on the board selling one. Save some bucks and know the parts work. There is a lot of junk out there so whoever you buy it from have them take it to a credible machine shop that knows Stage motors before buying one.
If it were me..... I'd wait until someone finally has a TA alum block running and see how it turns out... whether there are any problems with them and how much power they can hold. I'd build one of those. No shortage on parts as TA Performance is making these from scratch in a foundry. They are also making alum heads that should flow great. This cost will also surpass the $10K mark in a heartbeat as the blocks are $3K+ without any machining done. They are touting a 2000hp limit.... but no real testing aside from internet word of mouth has been really made public and proven. Noone is racing one that the turbo Buick community knows of.
Hope you have a big checkbook.... as Stage 2 stuff and TA aluminum block will be pricey.
A stock block prepped with billet girdle is safe to about 650-700hp before I would be really worried that it won't last long. Realize pushing any engine to the limit like this will require increased maintenance and shortened rebuild intervals. A new Eagle forged crank is $550 so this may be a more reasonable cost effective way to go.
If you want a bad ass Stage 2 setup here is a brand new setup that needs assembly and uses pretty much the best of the best.
http://www.turbobuick.com/forums/showthread.php?s=&threadid=111375
-GNX7
