Did any of the 1999 trucks have the Vortec 350? I don't think so, but I have a friend who swears that his is a Vortec 350. Was there a mid year change?
I haven't seen the truck so I have to go off of what he says...

 

1999 Tahoes and Suburbans have the 5.7 Vortec, I have a 1999 Tahoe.

 

Also in the 2500 and 3500 trucks in 1999 they still had the 350 vortec.

 

My grandfather bought a 99 K1500 Z71 old body style. I think there were just a few that were 99 year models with the old vortec 350. I guess these were produced after the 98 model year run, but before the new 99 models were into full production.

 

BigTex is right.
They had both the Classic Series pick-ups (K1500) with a 350 motor and the NBS Silverado 1500 pick-ups with the 327 offerred for 1999.

 

New body = new engine. 4.8, 5.3, 6.0

 

I once saw a an old body stile truck at a local dealer and saleman wanted to put money on the table that it was a 99.