if you want to do it on the cheap, you can do:
03/04 used cobra crank $250
03/04 used cobra rods $300
CP pistons $700
thats good to about 900HP or so. add a set of Billet I beam rods, and your capable of 1300HP.
but then you also have rings, headstuds, mainstuds, gaskets, machine work.
+1 i see alot of people forgeting the studs and rings... its the little **** you forget about that bites you... you wouldnt want a bolt on you rod or something snapping off that would be a no go