Also before taking the plunge look at some the gm sites I have been on ls1tech.com for a long time there is like 130,000 members there. Lots of stuff on there to check out. Personally I would look at a motor built by a speed shop and look a wrecked car to get the trans acessory and pcm from. ♥♥♥♥ for $10k you could get alot. If interested I can pm you some sites but you can get an ls3 stroked to a 418-427 for $7400. the other $3000 you save you could get everything else.
I personally have a whole bunch of LSx parts I have aquired over the years. I'm going to be running a 2005 forged LS2 with 2007 LS3/L92 heads and intake. I'm gonna use 2001 fbody acessories 2000 fbody wire harness and 2002 pcm, oh yeah a 2002 fbody t56 transmission.