Hypertech Power Programmer III for 1999 GM trucks with the 4.8/5.3/6.0. It was ordered for a 1999 Silverado with the 5.3 LS based small block. $50.00 + shipping. The programmer has been unlocked, the truck was turned back to stock prior to trade in.

The model number is 390302

PM if interested

 

will this also work for 4.3"s?

 

I don't think so the box says 99 GM Truck 4.8, 5.3, 6.0