The fact that it is a 99 motor, and a 4.3, will limit the amount of aftermkt performance parts. The motor is plenty peppy as produced and because of the many different stages of development that it has gone thru you must have a vin code to get the proper rebuild kit. The aftermkt can't keep up with all the small changes that obsolete previous parts. Such as the heads and intakes. There have been at least five different head castings since 93 on the "Vortec" 4.3 alone. Each one using a different intake and not interchangable with others. There have been several different changes in the pistons/rings, rod weights and materials. The cranks are balanced differently. All in the same size (4.3) engine.

Summit should be able to put together a "kit" for the rebuild. If not then Northern Automotive. If you still can't find one try Engine Parts in Desplains Ill. Talk to the owner "Tommy" he will help you out. They build custom engine kits for the engine builders/machine shops.

As for high perf parts.. When I did the shop truck the only affordable way to go was flat top pistons and 1.6 roller rockers. The cams, when available were mild and over $300.00 wholesale. No intakes were available, Headers were listed but I did not want the noise. Different size injectors and computer programs are available.

Anyone you talk with will need the year and VIN code. Possibly the build date.