[BobUnkefer]

Larry,
1998 was the transition year from LT1 to LS1. Early 98's had the LT1, later models had the LS1, mostly due to production availability from what I've been told.
GM certified the 98 model year for NHRA competition as an LT1 powertrain combination. That's the way the General wanted it I guess.

Hope this helps,

Unk