J-Rod,
What is the fastest thing you have personally owned and driven?
Jumping stright in to a twin turbo or big blower car/truck is not as easy as stabing and steering. Now if your wishing to start light with the boost down and work your way up, cool. I have seen too many people think that it is easy to do and don't. Start light but built strong and you will have fun for a long time.
Now to the rest of it
Marv can give you a ton of info on Gen 1 SBC.. Kevin (DJ) and Regan can probably keep things in order for big block stuff. As far as LS, Start with an LS3 block as it has the biggest bore and will let the heads move the most amount of air. If your are going to boost it, either use the stock crank or put a 4" crank in it, don't use a 4.10" as the wrist pin moves up the piston skirt weakening it. As far as heads go, Trick fFlow, SFR and Advanced Inductions (The head design used to be ETP's and are awesome heads but pricey).