Don't forget to add custom headers, driveshaft, ECU upgrade (not sure what the stock truck ECU can compensate for), injector upgrade (Stock ones might be good for 400HP), EFI fuel pump, surge tank, etc., etc.
Maybe put the L6 back in there just to have some fun with it next year while you are collecting V8 parts. I don't know about you, but after reading all of the threads about this project I'm dying to drive it! I can't imagine how you feel just looking at it in your garage! I can't go more than a few months without a track day, time trial, or autocross without going stir crazy (although GTR2 has been helping in that area this winter ).