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I am fairly sure the LQ4 or LQ9 will be your best bet, both of which are 6.0s.
Then again, if you are looking for some decent get up and go without spending a lot of money at the gas pump, a 5.3 will work out fine.
FOR ALL YOUR WHEEL, TIRE, AND ACCESSORY NEEDS
CONTACT: EPLEY'S TOUCH OF CLASSIC 1-270-843-6892
OR TO GET ME PERSONALLY CALL: 1-615-943-6514
2000 Chevy Silverado 4.8L RCSB: smoked UPD, Flowmaster exhaust, De-screened MAF, Nelson 93 hot tune. Upcoming installs: trans-go shift kit, Eaton posi, billet servo, ported and polished throttle body...Near future: 6.0/4L80E install with 150 wet shot