2000 Silverado ECSB- 5.3 CAI, Pacesetter LTs, ORY- Pipe, Flowmaster 50 series, E-fan, Ported T/B , Nelson Tuned, Built 4l60e, Circle D Stall, 3.42s G80, 2-4 Drop, Hertz Highs, Rockford 501s *Next* TURBO, 4L80e, and Tru Trac
i take it, youre wanting this for the 2000 ecsb?
do you not think the 5.3 would work for ya? with head work and a decent 220/220 or 226/226 cam ?
what size stall do you have?
get the true trac foresure and i would do a gear swap also 3:73 or 4:10's
or go 6.0 doesnt matter if its a lq9 or lq4, i hadnt raced my ecsb since i swapped to a rcsb, but i can honestly stay ot aint slow, with a stock motor flt trans dynatech headers, and a sweet tune
by the way its a lq4 with stock gears lol with dual exhaust 
i got to street race this truck ECSB) one time, and it was against a fully bolted ecsb if i had to guess it was a 5.3 cause i walked him like he was standing still 
basically you gotta ask yourself how fast ya wanna go and what would my ( your ) goals would be. putting together a fast ecsb isnt easy, theres very very few that i know of that run NA stewart being one and ap2002 being the other. the big picture is staying daily driven
then again just hook up the NOS and be done with it lol
Simple: 408 on steroids!
single digits coming soon!