Re: when was the ls1 put in the silverado?
No LS1 was ever put in the Silverado from the factory.
The Gen III (LS) SBC was introduced to the Silverado in 1999. They still made a few "classic" Silverados in 1999, which would have the old Gen II motors.
1997 Camaro SS #2703/2892 - LTs, 3" ORY, 2OTL, BBK 52mm, K&N, LCAs, Suspension
2004 Silverado Z71 - Summit White, CCSB, 285's, Leveled, Tint
2000 Honda CR250 - FMF Pipe, Renthal Bars, Barkbusters